How to execute a JavaScript function when I have its name as a string

Question

I have the name of a function in JavaScript as a string  How do I convert that into a function pointer so I can call it later   Depending on the circumstances  I may need to pass various arguments into the method too   Some of the functions may take the form of namespace namespace function args

User · Answer

Two things     avoid eval  it s terribly dangerous and slow secondly it doesn t matter where your function exists   global  -ness is irrelevant  x y foo   can be enabled through x y  foo     or x  y    foo     or even window  x    y    foo      You can chain indefinitely like this

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People keep saying that eval is dangerous and evil because it can run any arbitrary code  However  if you use eval with a whitelisting approach  assuming you know all the possible function names that may need to be run in advance  then eval is no longer a security concern because the input is no longer arbitrary  Whitelisting is a good and frequent security pattern  Here s an example    x000D   x000D  function runDynamicFn fnName     args    x000D       can also be fed from a tightly controlled config x000D    const allowedFnNames     fn1    ns1 ns2 fn3    ns4 fn4    x000D   x000D    return allowedFnNames includes fnName    eval fnName     args    undefined   x000D    x000D   x000D     test function  x000D  function fn1 a     x000D    console log  fn1 called with   a  x000D    x000D   x000D  runDynamicFn  alert  got you      x000D  runDynamicFn  fn1    foo   x000D   x000D   x000D

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Look basic   var namefunction    jspure      String  function jspure msg1       msg2            console log msg1  msg2         msg2            multiple argument     Results ur test window namefunction   hello   hello again       something    eval namefunction     hello      use string or something  but its eval just one argument and not exist multiple   Exist other type function is class and look example nils petersohn

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Here is my contribution to Jason Bunting s   Alex Nazarov s excellent answers  where I include error checking requested by Crashalot   Given this  contrived  preamble   a   function  args         console log   global func passed          for  var i   0  i  lt  arguments length  i               console log   - gt      arguments  i               ns       ns a   function  args         console log   namespace func passed          for  var i   0  i  lt  arguments length  i               console log   - gt      arguments  i                name    nsa   n s a      Snowden     noSuchAgency   function        then the following function   function executeFunctionByName  functionName  context     args            var args  namespaces  func       if  typeof functionName      undefined      throw  function name not specified          if  typeof eval  functionName        function      throw functionName     is not a function          if  typeof context      undefined               if  typeof context      object   amp  amp  context instanceof Array     false                  if  typeof context  functionName        function                      throw context         functionName     is not a function                             args   Array prototype slice call  arguments  2               else               args   Array prototype slice call  arguments  1                context   window                   else           context   window             namespaces   functionName split             func   namespaces pop         for  var i   0  i  lt  namespaces length  i               context   context  namespaces  i                 return context  func   apply  context  args        will allow you to call a javascript function by name stored in a string  either namespaced or global  with or without arguments  including Array objects   providing feedback on any errors encountered  hopefully catching them    The sample output shows how it works      calling a global function without parms executeFunctionByName   a          OUTPUT    global func passed           calling a global function passing a number  with implicit window context  executeFunctionByName   a   123         OUTPUT    global func passed    - gt  123          calling a namespaced function without parms executeFunctionByName   ns a          OUTPUT    namespace func passed           calling a namespaced function passing a string literal executeFunctionByName   ns a    No Such Agency           OUTPUT    namespace func passed    - gt  No Such Agency           calling a namespaced function  with explicit context as separate arg  passing a string literal and array  executeFunctionByName   a   ns   No Such Agency      007   is the man            OUTPUT    namespace func passed    - gt  No Such Agency    - gt  7 is the man          calling a global function passing a string variable  with implicit window context  executeFunctionByName   a   name         OUTPUT    global func passed    - gt  nsa          calling a non-existing function via string literal executeFunctionByName   n s a          OUTPUT    Uncaught n s a is not a function          calling a non-existing function by string variable executeFunctionByName  n s a         OUTPUT    Uncaught Snowden is not a function          calling an existing function with the wrong namespace reference executeFunctionByName   a              OUTPUT    Uncaught  object Object  a is not a function          calling no function executeFunctionByName         OUTPUT    Uncaught function name not specified          calling by empty string executeFunctionByName             OUTPUT    Uncaught  is not a function          calling an existing global function with a namespace reference executeFunctionByName   noSuchAgency   ns         OUTPUT    Uncaught  object Object  noSuchAgency is not a function

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Without using eval  function     you could to create a new function using new Function strName   The below code was tested using FF  Chrome  IE    lt html gt   lt body gt   lt button onclick  test    gt Try it lt  button gt   lt  body gt   lt  html gt   lt script type  text javascript  gt     function test         try               var fnName    myFunction             var fn   new Function fnName           fn            catch  err            console log  error   err message                  function myFunction         console log  Executing myFunction            lt  script gt

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With ES6 you could to access class methods by name   class X     method1        console log  1          method2        this  method1          console log  2          let x    new X    x  method2        the output would be   1 2

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Just thought I d post a slightly altered version of Jason Bunting s very helpful function   First  I have simplified the first statement by supplying a second parameter to slice    The original version was working fine in all browsers except IE   Second  I have replaced this with context in the return statement  otherwise  this was always pointing to window when the target function was being executed   function executeFunctionByName functionName  context     args           var args   Array prototype slice call arguments  2       var namespaces   functionName split           var func   namespaces pop        for  var i   0  i  lt  namespaces length  i              context   context namespaces i              return context func  apply context  args

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With ES6 you could to access class methods by name   class X     method1        console log  1          method2        this  method1          console log  2          let x    new X    x  method2        the output would be   1 2

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There s a very similar thing in my code  I have a server-generated string which contains a function name which I need to pass as a callback for a 3rd party library  So I have a code that takes the string and returns a  pointer  to the function  or null if it isn t found   My solution was very similar to  Jason Bunting s very helpful function     although it doesn t auto-execute  and the context is always on the window  But this can be easily modified   Hopefully this will be helpful to someone          Converts a string containing a function or object method name to a function pointer      param  string   func     return function     function getFuncFromString func           if already a function  return     if  typeof func      function   return func          if string  try to find function or method of object  of  obj func  format      if  typeof func      string             if   func length  return null          var target   window          var func   func split               while  func length                var ns   func shift                if  typeof target ns       undefined   return null              target   target ns                     if  typeof target      function   return target                return null if could not parse     return null

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So  like others said  definitely the best option is   window  myfunction   arguments    And like Jason Bunting said  it won t work if the name of your function includes an object   window  myobject myfunction   arguments      won t work window  myobject    myfunction   arguments      will work   So here s my version of a function that will execute all functions by name  including an object or not     x000D   x000D  my     x000D      code     x000D          is     x000D              nice   function a  b   alert a         b     x000D            x000D        x000D     x000D   x000D  guy   function    alert  awesome      x000D   x000D  function executeFunctionByName str  args  x000D    x000D      var arr   str split       x000D      var fn   window  arr 0     x000D       x000D      for  var i   1  i  lt  arr length  i    x000D        fn   fn  arr i       x000D      fn apply window  args   x000D    x000D   x000D  executeFunctionByName  my code is nice     arg1    arg2     x000D  executeFunctionByName  guy    x000D   x000D   x000D

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There are several executeByName functions here which works fine  unless name contains square brackets - issue I ran into - as I have dynamically generated names  So above functions will fail on names like  app widget  872LfCHc    toggleFolders    As a remedy  I ve made function to take this into account too  maybe someone will find it usefull   Generated from CoffeeScript   var executeByName   function name  context      var args  func  i  j  k  len  len1  n  normalizedName  ns    if  context    null        context   window        args   Array prototype slice call arguments  2     normalizedName   name replace         g      replace     g          ns   normalizedName split         func   context    for  i   j   0  len   ns length  j  lt  len  i     j        n   ns i       func   func n         ns pop      for  i   k   0  len1   ns length  k  lt  len1  i     k        n   ns i       context   context n         if  typeof func      function         throw new TypeError  Cannot execute function     name         return func apply context  args       For better readability check also CoffeeScript version   executeByName    name  context   window  - gt      args   Array prototype slice call arguments  2      normalizedName   name replace         g      replace     g           ns   normalizedName split         func   context     for n  i in ns         func   func n       ns pop       for n  i in ns         context   context n       if typeof func     function          throw new TypeError  Cannot execute function     name     func apply context  args

User · Answer

People keep saying that eval is dangerous and evil because it can run any arbitrary code  However  if you use eval with a whitelisting approach  assuming you know all the possible function names that may need to be run in advance  then eval is no longer a security concern because the input is no longer arbitrary  Whitelisting is a good and frequent security pattern  Here s an example    x000D   x000D  function runDynamicFn fnName     args    x000D       can also be fed from a tightly controlled config x000D    const allowedFnNames     fn1    ns1 ns2 fn3    ns4 fn4    x000D   x000D    return allowedFnNames includes fnName    eval fnName     args    undefined   x000D    x000D   x000D     test function  x000D  function fn1 a     x000D    console log  fn1 called with   a  x000D    x000D   x000D  runDynamicFn  alert  got you      x000D  runDynamicFn  fn1    foo   x000D   x000D   x000D

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I can t resist mentioning another trick  which helps if you have an unknown number of arguments that are also being passed as part of the string containing the function name  For example   var annoyingstring    call my func 123  true   blah      If your Javascript is running on a HTML page  all you need is an invisible link  you can pass a string into the onclick attribute  and the call the click method    lt a href     id  link secret  gt  lt  -- invisible -- gt  lt  a gt       link secret   attr  onclick   annoyingstring       link secret   click      Or create the  lt a gt  element at runtime

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All the answers assume that the functions can be accessed through global scope  window   However  the OP did not make this assumption   If the functions live in a local scope  aka closure  and are not referenced by some other local object  bad luck  You have to use eval   AFAIK  see dynamically call local function in javascript

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If you want to call a function of an object instead of a global function with window  functionName    You can do it like   var myObject new Object    myObject  functionName   arguments     Example   var now new Date    now  getFullYear

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The answer to this other question shows you how to do that  Javascript equivalent of Python  39 s locals     Basically  you can say  window  foo   arg1  arg2     or as many others have suggested  you can just use eval   eval fname  arg1  arg2     although this is extremely unsafe unless you re absolutely sure about what you re eval-ing

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Here is my Es6 approach which enables you to call your function by it s name as string or it s function name and also enable you to pass different numbers of arguments to different types of functions    x000D   x000D  function fnCall fn     args  x000D    x000D    let func    typeof fn    string   window fn  fn  x000D    if  typeof func     function   func    args   x000D    else throw new Error    fn  is Not a function     x000D    x000D   x000D   x000D  function example1 arg1  console log arg1   x000D  function example2 arg1  arg2  console log arg1      and       arg2   x000D  function example3   console log  No arguments     x000D   x000D  fnCall  example1    test 1    x000D  fnCall  example2    test 2    test3    x000D  fnCall example3   x000D  fnCall  example4       should raise an error in console x000D   x000D   x000D

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I think an elegant way of doing this is by defining your functions in a hash object  Then you can have a reference to those functions from the hash using the string  e g  var customObject       customFunction  function param           Then you can call  customObject  customFunction   param    Where customFunction will be a string matching a function defined in your object  UPDATE It seems that this answer was helpful for many fellow coders out there so here goes an updated version  With ES6 you can additionally use Computed Property Names which will allow you to avoid magic strings   x000D   x000D  const FunctionNames   Object freeze      FirstFunction   firstFunction      SecondFunction   secondFunction             var customObject        FunctionNames FirstFunction   function param           FunctionNames SecondFunction   function param                customObject FunctionNames FirstFunction  param   x000D   x000D   x000D

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I don t think you need complicated intermediate functions or eval or be dependent on global variables like window  function fun1 arg      console log arg      function fun2 arg      console log arg      const operations       fun1    fun2     operations  quot fun1 quot    quot Hello World quot    operations fun2  quot Hello World quot        You can use intermediate variables  if you like let temp    quot fun1 quot   operations temp   quot Hello World quot     It will also work with imported functions     mode js export function fun1 arg      console log arg      export function fun2 arg      console log arg         index js import   fun1  fun2   from  quot   mod quot    const operations       fun1    fun2     operations  quot fun1 quot    quot Hello World quot    operations  quot fun2 quot    quot Hello World quot     Since it is using property access  it will survive minimization or obfuscation  contrary to some answers you will find here

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Depending on where you are you can also use   this  funcname      self  funcname      window  funcname      top  funcname      globalThis  funcname        or  in nodejs  global  funcname

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All the answers assume that the functions can be accessed through global scope  window   However  the OP did not make this assumption   If the functions live in a local scope  aka closure  and are not referenced by some other local object  bad luck  You have to use eval   AFAIK  see dynamically call local function in javascript

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I think an elegant way of doing this is by defining your functions in a hash object  Then you can have a reference to those functions from the hash using the string  e g  var customObject       customFunction  function param           Then you can call  customObject  customFunction   param    Where customFunction will be a string matching a function defined in your object  UPDATE It seems that this answer was helpful for many fellow coders out there so here goes an updated version  With ES6 you can additionally use Computed Property Names which will allow you to avoid magic strings   x000D   x000D  const FunctionNames   Object freeze      FirstFunction   firstFunction      SecondFunction   secondFunction             var customObject        FunctionNames FirstFunction   function param           FunctionNames SecondFunction   function param                customObject FunctionNames FirstFunction  param   x000D   x000D   x000D

User · Answer

Here is my contribution to Jason Bunting s   Alex Nazarov s excellent answers  where I include error checking requested by Crashalot   Given this  contrived  preamble   a   function  args         console log   global func passed          for  var i   0  i  lt  arguments length  i               console log   - gt      arguments  i               ns       ns a   function  args         console log   namespace func passed          for  var i   0  i  lt  arguments length  i               console log   - gt      arguments  i                name    nsa   n s a      Snowden     noSuchAgency   function        then the following function   function executeFunctionByName  functionName  context     args            var args  namespaces  func       if  typeof functionName      undefined      throw  function name not specified          if  typeof eval  functionName        function      throw functionName     is not a function          if  typeof context      undefined               if  typeof context      object   amp  amp  context instanceof Array     false                  if  typeof context  functionName        function                      throw context         functionName     is not a function                             args   Array prototype slice call  arguments  2               else               args   Array prototype slice call  arguments  1                context   window                   else           context   window             namespaces   functionName split             func   namespaces pop         for  var i   0  i  lt  namespaces length  i               context   context  namespaces  i                 return context  func   apply  context  args        will allow you to call a javascript function by name stored in a string  either namespaced or global  with or without arguments  including Array objects   providing feedback on any errors encountered  hopefully catching them    The sample output shows how it works      calling a global function without parms executeFunctionByName   a          OUTPUT    global func passed           calling a global function passing a number  with implicit window context  executeFunctionByName   a   123         OUTPUT    global func passed    - gt  123          calling a namespaced function without parms executeFunctionByName   ns a          OUTPUT    namespace func passed           calling a namespaced function passing a string literal executeFunctionByName   ns a    No Such Agency           OUTPUT    namespace func passed    - gt  No Such Agency           calling a namespaced function  with explicit context as separate arg  passing a string literal and array  executeFunctionByName   a   ns   No Such Agency      007   is the man            OUTPUT    namespace func passed    - gt  No Such Agency    - gt  7 is the man          calling a global function passing a string variable  with implicit window context  executeFunctionByName   a   name         OUTPUT    global func passed    - gt  nsa          calling a non-existing function via string literal executeFunctionByName   n s a          OUTPUT    Uncaught n s a is not a function          calling a non-existing function by string variable executeFunctionByName  n s a         OUTPUT    Uncaught Snowden is not a function          calling an existing function with the wrong namespace reference executeFunctionByName   a              OUTPUT    Uncaught  object Object  a is not a function          calling no function executeFunctionByName         OUTPUT    Uncaught function name not specified          calling by empty string executeFunctionByName             OUTPUT    Uncaught  is not a function          calling an existing global function with a namespace reference executeFunctionByName   noSuchAgency   ns         OUTPUT    Uncaught  object Object  noSuchAgency is not a function

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all you have to do is use a context or define a new context where you function s  reside   you are not limited to window  f       here is an example of how I use some dynamic invocation for some REST services       Author  Hugo Reyes   www teamsrunner com           function   W  D       enclose it as self invoking function to avoid name collisions           to call function1 as string        initialize your FunctionHUB as your namespace - context        you can use W  functionX      if you want to call a function at the window scope      var container   new FunctionHUB             call a function1 by name with one parameter       container  function1     Hugo              call a function2 by name      container  function2     Hugo Leon             OO style class     function FunctionHUB              this function1   function  name                 console log  Hi     name     inside function 1                      this function2   function  name                 console log  Hi    name     inside function 2                        window  document      in case you need window context inside your namespace    If you want to generate the entire function from a string  that s a different answer  also please notice that you are not limited to a single name space   if you name space exists as   my name space for functions etc etc etc the last branch of your name space contains the function as my name space for functions etc etc  function       Hope it helps  H

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Two things     avoid eval  it s terribly dangerous and slow secondly it doesn t matter where your function exists   global  -ness is irrelevant  x y foo   can be enabled through x y  foo     or x  y    foo     or even window  x    y    foo      You can chain indefinitely like this

User · Answer

Easiest way is to access it like has element   window ClientSideValidations forms location form   is same as   window ClientSideValidations forms  location form

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Here is my Es6 approach which enables you to call your function by it s name as string or it s function name and also enable you to pass different numbers of arguments to different types of functions    x000D   x000D  function fnCall fn     args  x000D    x000D    let func    typeof fn    string   window fn  fn  x000D    if  typeof func     function   func    args   x000D    else throw new Error    fn  is Not a function     x000D    x000D   x000D   x000D  function example1 arg1  console log arg1   x000D  function example2 arg1  arg2  console log arg1      and       arg2   x000D  function example3   console log  No arguments     x000D   x000D  fnCall  example1    test 1    x000D  fnCall  example2    test 2    test3    x000D  fnCall example3   x000D  fnCall  example4       should raise an error in console x000D   x000D   x000D

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Just thought I d post a slightly altered version of Jason Bunting s very helpful function   First  I have simplified the first statement by supplying a second parameter to slice    The original version was working fine in all browsers except IE   Second  I have replaced this with context in the return statement  otherwise  this was always pointing to window when the target function was being executed   function executeFunctionByName functionName  context     args           var args   Array prototype slice call arguments  2       var namespaces   functionName split           var func   namespaces pop        for  var i   0  i  lt  namespaces length  i              context   context namespaces i              return context func  apply context  args

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Easiest way is to access it like has element   window ClientSideValidations forms location form   is same as   window ClientSideValidations forms  location form

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Thanks for the very helpful answer  I m using Jason Bunting s function in my projects    I extended it to use it with an optional timeout  because the normal way to set a timeout wont work  See abhishekisnot s question   x000D   x000D  function executeFunctionByName functionName  context  timeout     args        x000D   var args   Array prototype slice call arguments  3   x000D   var namespaces   functionName split       x000D   var func   namespaces pop    x000D   for  var i   0  i  lt  namespaces length  i      x000D    context   context namespaces i    x000D     x000D   var timeoutID   setTimeout  x000D    function    context func  apply context  args    x000D    timeout x000D      x000D      return timeoutID  x000D    x000D   x000D  var  very     x000D       deeply    x000D           defined    x000D               function  function num1  num2    x000D                  console log  Execution  very  deeply  defined  function      num1  num2   x000D                x000D            x000D        x000D    x000D   x000D  console log  now wait   x000D  executeFunctionByName   very  deeply  defined  function   window  2000  40  50    x000D   x000D   x000D

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The answer to this other question shows you how to do that  Javascript equivalent of Python  39 s locals     Basically  you can say  window  foo   arg1  arg2     or as many others have suggested  you can just use eval   eval fname  arg1  arg2     although this is extremely unsafe unless you re absolutely sure about what you re eval-ing

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Could you not just do this   var codeToExecute    My Namespace functionName     var tmpFunc   new Function codeToExecute   tmpFunc      You can also execute any other JavaScript using this method

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There s a very similar thing in my code  I have a server-generated string which contains a function name which I need to pass as a callback for a 3rd party library  So I have a code that takes the string and returns a  pointer  to the function  or null if it isn t found   My solution was very similar to  Jason Bunting s very helpful function     although it doesn t auto-execute  and the context is always on the window  But this can be easily modified   Hopefully this will be helpful to someone          Converts a string containing a function or object method name to a function pointer      param  string   func     return function     function getFuncFromString func           if already a function  return     if  typeof func      function   return func          if string  try to find function or method of object  of  obj func  format      if  typeof func      string             if   func length  return null          var target   window          var func   func split               while  func length                var ns   func shift                if  typeof target ns       undefined   return null              target   target ns                     if  typeof target      function   return target                return null if could not parse     return null

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Don t use eval unless you absolutely  positively have no other choice   As has been mentioned  using something like this would be the best way to do it   window  functionName   arguments     That  however  will not work with a namespace d function   window  My Namespace functionName   arguments      fail   This is how you would do that   window  My    Namespace    functionName   arguments      succeeds   In order to make that easier and provide some flexibility  here is a convenience function   function executeFunctionByName functionName  context     args         var args   Array prototype slice call arguments  2     var namespaces   functionName split         var func   namespaces pop      for var i   0  i  lt  namespaces length  i          context   context namespaces i          return context func  apply context  args       You would call it like so   executeFunctionByName  My Namespace functionName   window  arguments     Note  you can pass in whatever context you want  so this would do the same as above   executeFunctionByName  Namespace functionName   My  arguments

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So  like others said  definitely the best option is   window  myfunction   arguments    And like Jason Bunting said  it won t work if the name of your function includes an object   window  myobject myfunction   arguments      won t work window  myobject    myfunction   arguments      will work   So here s my version of a function that will execute all functions by name  including an object or not     x000D   x000D  my     x000D      code     x000D          is     x000D              nice   function a  b   alert a         b     x000D            x000D        x000D     x000D   x000D  guy   function    alert  awesome      x000D   x000D  function executeFunctionByName str  args  x000D    x000D      var arr   str split       x000D      var fn   window  arr 0     x000D       x000D      for  var i   1  i  lt  arr length  i    x000D        fn   fn  arr i       x000D      fn apply window  args   x000D    x000D   x000D  executeFunctionByName  my code is nice     arg1    arg2     x000D  executeFunctionByName  guy    x000D   x000D   x000D

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Thanks for the very helpful answer  I m using Jason Bunting s function in my projects    I extended it to use it with an optional timeout  because the normal way to set a timeout wont work  See abhishekisnot s question   x000D   x000D  function executeFunctionByName functionName  context  timeout     args        x000D   var args   Array prototype slice call arguments  3   x000D   var namespaces   functionName split       x000D   var func   namespaces pop    x000D   for  var i   0  i  lt  namespaces length  i      x000D    context   context namespaces i    x000D     x000D   var timeoutID   setTimeout  x000D    function    context func  apply context  args    x000D    timeout x000D      x000D      return timeoutID  x000D    x000D   x000D  var  very     x000D       deeply    x000D           defined    x000D               function  function num1  num2    x000D                  console log  Execution  very  deeply  defined  function      num1  num2   x000D                x000D            x000D        x000D    x000D   x000D  console log  now wait   x000D  executeFunctionByName   very  deeply  defined  function   window  2000  40  50    x000D   x000D   x000D

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You just need convert your string to a pointer by window  lt method name gt    example   var function name    string   function name   window function name     and now you can use it like a pointer

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Since eval   is evil  and new Function   is not the most efficient way to achieve this  here is a quick JS function that returns the function from its name in string    Works for namespace d functions Fallbacks to null-function in case of null undefined string Fallbacks to null-function if function not found         function convertStringtoFunction functionName            var nullFunc   function         Fallback Null-Function         var ret   window     Top level namespace             If null undefined string  then return a Null-Function         if functionName  null  return nullFunc              Convert string to function name         functionName split      forEach function key   ret   ret key                   If function name is not available  then return a Null-Function else the actual function         return  ret  null   nullFunc   ret             Usage         convertStringtoFunction  level1 midLevel myFunction   arg1  arg2

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This is working for me   var command    Add   var tempFunction   new Function  Arg1   Arg2    window     command     Arg1 Arg2     tempFunction x y     I hope this works

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Don t use eval unless you absolutely  positively have no other choice   As has been mentioned  using something like this would be the best way to do it   window  functionName   arguments     That  however  will not work with a namespace d function   window  My Namespace functionName   arguments      fail   This is how you would do that   window  My    Namespace    functionName   arguments      succeeds   In order to make that easier and provide some flexibility  here is a convenience function   function executeFunctionByName functionName  context     args         var args   Array prototype slice call arguments  2     var namespaces   functionName split         var func   namespaces pop      for var i   0  i  lt  namespaces length  i          context   context namespaces i          return context func  apply context  args       You would call it like so   executeFunctionByName  My Namespace functionName   window  arguments     Note  you can pass in whatever context you want  so this would do the same as above   executeFunctionByName  Namespace functionName   My  arguments

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BE CAREFUL     One should try to avoid calling a function by string in JavaScript for two reasons   Reason 1  Some code obfuscators will wreck your code as they will change the function names  making the string invalid   Reason 2  It is much harder to maintain code that uses this methodology as it is much harder to locate usages of the methods called by a string

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You can call javascript function within the eval  functionname as string   either  Like below   eval is pure javascript function   function testfunc        return  hello world         document   ready function              div   html eval  testfunc           Working example  https   jsfiddle net suatatan 24ms0fna 4

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Since eval   is evil  and new Function   is not the most efficient way to achieve this  here is a quick JS function that returns the function from its name in string    Works for namespace d functions Fallbacks to null-function in case of null undefined string Fallbacks to null-function if function not found         function convertStringtoFunction functionName            var nullFunc   function         Fallback Null-Function         var ret   window     Top level namespace             If null undefined string  then return a Null-Function         if functionName  null  return nullFunc              Convert string to function name         functionName split      forEach function key   ret   ret key                   If function name is not available  then return a Null-Function else the actual function         return  ret  null   nullFunc   ret             Usage         convertStringtoFunction  level1 midLevel myFunction   arg1  arg2

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The answer to this other question shows you how to do that  Javascript equivalent of Python  39 s locals     Basically  you can say  window  foo   arg1  arg2     or as many others have suggested  you can just use eval   eval fname  arg1  arg2     although this is extremely unsafe unless you re absolutely sure about what you re eval-ing

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To add to Jason Bunting s answer  if you re using nodejs or something  and this works in dom js  too   you could use this instead of window  and remember  eval is evil   this  fun   ctionName

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To add to Jason Bunting s answer  if you re using nodejs or something  and this works in dom js  too   you could use this instead of window  and remember  eval is evil   this  fun   ctionName

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I can t resist mentioning another trick  which helps if you have an unknown number of arguments that are also being passed as part of the string containing the function name  For example   var annoyingstring    call my func 123  true   blah      If your Javascript is running on a HTML page  all you need is an invisible link  you can pass a string into the onclick attribute  and the call the click method    lt a href     id  link secret  gt  lt  -- invisible -- gt  lt  a gt       link secret   attr  onclick   annoyingstring       link secret   click      Or create the  lt a gt  element at runtime

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Two things     avoid eval  it s terribly dangerous and slow secondly it doesn t matter where your function exists   global  -ness is irrelevant  x y foo   can be enabled through x y  foo     or x  y    foo     or even window  x    y    foo      You can chain indefinitely like this

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BE CAREFUL     One should try to avoid calling a function by string in JavaScript for two reasons   Reason 1  Some code obfuscators will wreck your code as they will change the function names  making the string invalid   Reason 2  It is much harder to maintain code that uses this methodology as it is much harder to locate usages of the methods called by a string

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This is working for me   var command    Add   var tempFunction   new Function  Arg1   Arg2    window     command     Arg1 Arg2     tempFunction x y     I hope this works

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Look basic   var namefunction    jspure      String  function jspure msg1       msg2            console log msg1  msg2         msg2            multiple argument     Results ur test window namefunction   hello   hello again       something    eval namefunction     hello      use string or something  but its eval just one argument and not exist multiple   Exist other type function is class and look example nils petersohn

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Without using eval  function     you could to create a new function using new Function strName   The below code was tested using FF  Chrome  IE    lt html gt   lt body gt   lt button onclick  test    gt Try it lt  button gt   lt  body gt   lt  html gt   lt script type  text javascript  gt     function test         try               var fnName    myFunction             var fn   new Function fnName           fn            catch  err            console log  error   err message                  function myFunction         console log  Executing myFunction            lt  script gt

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I don t think you need complicated intermediate functions or eval or be dependent on global variables like window  function fun1 arg      console log arg      function fun2 arg      console log arg      const operations       fun1    fun2     operations  quot fun1 quot    quot Hello World quot    operations fun2  quot Hello World quot        You can use intermediate variables  if you like let temp    quot fun1 quot   operations temp   quot Hello World quot     It will also work with imported functions     mode js export function fun1 arg      console log arg      export function fun2 arg      console log arg         index js import   fun1  fun2   from  quot   mod quot    const operations       fun1    fun2     operations  quot fun1 quot    quot Hello World quot    operations  quot fun2 quot    quot Hello World quot     Since it is using property access  it will survive minimization or obfuscation  contrary to some answers you will find here

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Surprised to see no mention of setTimeout   To run a function without arguments   var functionWithoutArguments   function        console log  Executing functionWithoutArguments      setTimeout  functionWithoutArguments     0     To run function with arguments   var functionWithArguments   function arg1  arg2        console log  Executing functionWithArguments   arg1  arg2     setTimeout  functionWithArguments 10  20       To run deeply namespaced function   var  very          deeply             defined                 function  function num1  num2                    console log  Execution  very  deeply  defined  function      num1  num2                                   setTimeout   very  deeply  defined  function 40 50    0

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You can call javascript function within the eval  functionname as string   either  Like below   eval is pure javascript function   function testfunc        return  hello world         document   ready function              div   html eval  testfunc           Working example  https   jsfiddle net suatatan 24ms0fna 4

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Could you not just do this   var codeToExecute    My Namespace functionName     var tmpFunc   new Function codeToExecute   tmpFunc      You can also execute any other JavaScript using this method

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all you have to do is use a context or define a new context where you function s  reside   you are not limited to window  f       here is an example of how I use some dynamic invocation for some REST services       Author  Hugo Reyes   www teamsrunner com           function   W  D       enclose it as self invoking function to avoid name collisions           to call function1 as string        initialize your FunctionHUB as your namespace - context        you can use W  functionX      if you want to call a function at the window scope      var container   new FunctionHUB             call a function1 by name with one parameter       container  function1     Hugo              call a function2 by name      container  function2     Hugo Leon             OO style class     function FunctionHUB              this function1   function  name                 console log  Hi     name     inside function 1                      this function2   function  name                 console log  Hi    name     inside function 2                        window  document      in case you need window context inside your namespace    If you want to generate the entire function from a string  that s a different answer  also please notice that you are not limited to a single name space   if you name space exists as   my name space for functions etc etc etc the last branch of your name space contains the function as my name space for functions etc etc  function       Hope it helps  H

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Depending on where you are you can also use   this  funcname      self  funcname      window  funcname      top  funcname      globalThis  funcname        or  in nodejs  global  funcname

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The answer to this other question shows you how to do that  Javascript equivalent of Python  39 s locals     Basically  you can say  window  foo   arg1  arg2     or as many others have suggested  you can just use eval   eval fname  arg1  arg2     although this is extremely unsafe unless you re absolutely sure about what you re eval-ing

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There are several executeByName functions here which works fine  unless name contains square brackets - issue I ran into - as I have dynamically generated names  So above functions will fail on names like  app widget  872LfCHc    toggleFolders    As a remedy  I ve made function to take this into account too  maybe someone will find it usefull   Generated from CoffeeScript   var executeByName   function name  context      var args  func  i  j  k  len  len1  n  normalizedName  ns    if  context    null        context   window        args   Array prototype slice call arguments  2     normalizedName   name replace         g      replace     g          ns   normalizedName split         func   context    for  i   j   0  len   ns length  j  lt  len  i     j        n   ns i       func   func n         ns pop      for  i   k   0  len1   ns length  k  lt  len1  i     k        n   ns i       context   context n         if  typeof func      function         throw new TypeError  Cannot execute function     name         return func apply context  args       For better readability check also CoffeeScript version   executeByName    name  context   window  - gt      args   Array prototype slice call arguments  2      normalizedName   name replace         g      replace     g           ns   normalizedName split         func   context     for n  i in ns         func   func n       ns pop       for n  i in ns         context   context n       if typeof func     function          throw new TypeError  Cannot execute function     name     func apply context  args

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One more detail on Jason and Alex s posts  I found it helpful to add a default value to context  Just put context   context    undefined  window context  at the beginning of the function  You can change window to whatever your preferred context is  and then you won t need to pass in the same variable each time you call this in your default context

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Don t use eval unless you absolutely  positively have no other choice   As has been mentioned  using something like this would be the best way to do it   window  functionName   arguments     That  however  will not work with a namespace d function   window  My Namespace functionName   arguments      fail   This is how you would do that   window  My    Namespace    functionName   arguments      succeeds   In order to make that easier and provide some flexibility  here is a convenience function   function executeFunctionByName functionName  context     args         var args   Array prototype slice call arguments  2     var namespaces   functionName split         var func   namespaces pop      for var i   0  i  lt  namespaces length  i          context   context namespaces i          return context func  apply context  args       You would call it like so   executeFunctionByName  My Namespace functionName   window  arguments     Note  you can pass in whatever context you want  so this would do the same as above   executeFunctionByName  Namespace functionName   My  arguments

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There too some very helpful way   http   devlicio us blogs sergio pereira archive 2009 02 09 javascript-5-ways-to-call-a-function aspx  var arrayMaker           someProperty   some value here         make  function  arg1  arg2              return   this  arg1  arg2                 execute  function name

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Two things     avoid eval  it s terribly dangerous and slow secondly it doesn t matter where your function exists   global  -ness is irrelevant  x y foo   can be enabled through x y  foo     or x  y    foo     or even window  x    y    foo      You can chain indefinitely like this

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Surprised to see no mention of setTimeout   To run a function without arguments   var functionWithoutArguments   function        console log  Executing functionWithoutArguments      setTimeout  functionWithoutArguments     0     To run function with arguments   var functionWithArguments   function arg1  arg2        console log  Executing functionWithArguments   arg1  arg2     setTimeout  functionWithArguments 10  20       To run deeply namespaced function   var  very          deeply             defined                 function  function num1  num2                    console log  Execution  very  deeply  defined  function      num1  num2                                   setTimeout   very  deeply  defined  function 40 50    0

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let t0        gt    alert  red0       var t1        gt   alert  red1       var t2        gt   alert  red2       var t3        gt   alert  red3       var t4        gt   alert  red4       var t5        gt   alert  red5       var t6        gt   alert  red6        function getSelection type        var evalSelection            title0   t0         title1   t1         title2   t2         title3   t3         title4   t4         title5   t5         title6   t6         default   function             return  Default                      return  evalSelection type     evalSelection  default             getSelection  title1      A more OOP solution

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let t0        gt    alert  red0       var t1        gt   alert  red1       var t2        gt   alert  red2       var t3        gt   alert  red3       var t4        gt   alert  red4       var t5        gt   alert  red5       var t6        gt   alert  red6        function getSelection type        var evalSelection            title0   t0         title1   t1         title2   t2         title3   t3         title4   t4         title5   t5         title6   t6         default   function             return  Default                      return  evalSelection type     evalSelection  default             getSelection  title1      A more OOP solution

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There too some very helpful way   http   devlicio us blogs sergio pereira archive 2009 02 09 javascript-5-ways-to-call-a-function aspx  var arrayMaker           someProperty   some value here         make  function  arg1  arg2              return   this  arg1  arg2                 execute  function name

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One more detail on Jason and Alex s posts  I found it helpful to add a default value to context  Just put context   context    undefined  window context  at the beginning of the function  You can change window to whatever your preferred context is  and then you won t need to pass in the same variable each time you call this in your default context

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You just need convert your string to a pointer by window  lt method name gt    example   var function name    string   function name   window function name     and now you can use it like a pointer

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Don t use eval unless you absolutely  positively have no other choice   As has been mentioned  using something like this would be the best way to do it   window  functionName   arguments     That  however  will not work with a namespace d function   window  My Namespace functionName   arguments      fail   This is how you would do that   window  My    Namespace    functionName   arguments      succeeds   In order to make that easier and provide some flexibility  here is a convenience function   function executeFunctionByName functionName  context     args         var args   Array prototype slice call arguments  2     var namespaces   functionName split         var func   namespaces pop      for var i   0  i  lt  namespaces length  i          context   context namespaces i          return context func  apply context  args       You would call it like so   executeFunctionByName  My Namespace functionName   window  arguments     Note  you can pass in whatever context you want  so this would do the same as above   executeFunctionByName  Namespace functionName   My  arguments

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If you want to call a function of an object instead of a global function with window  functionName    You can do it like   var myObject new Object    myObject  functionName   arguments     Example   var now new Date    now  getFullYear

[javascript] How to execute a JavaScript function when I have its name as a string

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