How to turn a String into a JavaScript function call

Question

I got a string like   settings functionName         t parentNode id          that I want to translate into a function call like so   clickedOnItem IdofParent     This of course will have to be done in JavaScript   When I do an alert on settings functionName         t parentNode id        it seems to get everything correct   I just need to call the function that it would translate into   Legend   settings functionName   clickedOnItem  t parentNode id   IdofParent

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eval  javascript code      it is extensively used when dealing with JSON

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Seeing as I hate eval  and I am not alone   var fn   window settings functionName   if typeof fn      function         fn t parentNode id       Edit  In reply to  Mahan s comment  In this particular case  settings functionName would be  clickedOnItem   This would  at runtime translate var fn   window settings functionName   into var fn   window  clickedOnItem    which would obtain a reference to function clickedOnItem  nodeId      Once we have a reference to a function inside a variable  we can call this function by  calling the variable   i e  fn t parentNode id   which equals clickedOnItem t parentNode id   which was what the OP wanted   More full example      Somewhere     window settings               Other settings      functionName   clickedOnItem              More settings           Later    function clickedOnItem  nodeId         Some cool event handling code here          Even later    var fn   window settings functionName       note that settings functionName could also be written    as window settings functionName  In this case  we use the fact that window    is the implied scope of global variables     if typeof fn      function         fn t parentNode id

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Here is a more generic way to do the same  while supporting scopes       Get function from string  with or without scopes  by Nicolas Gauthier  window getFunctionFromString   function string        var scope   window      var scopeSplit   string split           for  i   0  i  lt  scopeSplit length - 1  i                  scope   scope scopeSplit i             if  scope    undefined  return             return scope scopeSplit scopeSplit length - 1        Hope it can help some people out

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If settings functionName is already a function  you could do this   settings functionName t parentNode id     Otherwise this should also work if settings functionName is just the name of the function   if  typeof window settings functionName      function         window settings functionName  t parentNode id

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Based on Nicolas Gauthier answer   var strng    someobj someCallback   var data    someData    var func   window  var funcSplit   strng split       for i   0 i  lt  funcSplit length i          We maybe can check typeof and break the bucle if typeof    function    func   func funcSplit i      func data

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I prefer to use something like this   window callbackClass  newFunctionName     function data    console log data         window callbackClass  newFunctionName   data

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JavaScript has an eval function that evaluates a string and executes it as code   eval settings functionName         t parentNode id

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I wanted to be able to take a function name as a string  call it  AND pass an argument to the function  I couldn t get the selected answer for this question to do that  but this answer explained it exactly  and here is a short demo   function test function argument           alert  This function     argument       functionName    test function    window functionName   works       This also works with multiple arguments

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window settings functionName  t parentNode id     No need for an eval

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In javascript that uses the CommonJS spec  like node js for instance you can do what I show below  Which is pretty handy for accessing a variable by a string even if its not defined on the window object  If there is a class named MyClass  defined within a CommonJS module named MyClass js     MyClass js var MyClass   function            I do stuff in here  Probably return an object     return          foo   bar           module exports   MyClass    You can then do this nice bit o witchcraft from another file called MyOtherFile js     MyOtherFile js  var myString    MyClass    var MyClass   require        myString   var obj   new MyClass     console log obj foo      returns  bar    One more reason why CommonJS is such a pleasure

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This took me a while to figure out  as the conventional window  someFunctionName     did not work for me at first   The names of my functions were being pulled as an AJAX response from a database   Also  for whatever reason  my functions were declared outside of the scope of the window  so in order to fix this I had to rewrite the functions I was calling from  function someFunctionName        to  window someFunctionName   function        and from there I could call window  someFunctionName     with ease   I hope this helps someone

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While I like the first answer and I hate eval  I d like to add that there s another way  similar to eval  so if you can go around it and not use it  you better do  But in some cases you may want to call some javascript code before or after some ajax call and if you have this code in a custom attribute instead of ajax you could use this       var executeBefore     el  attr  data-execute-before-ajax        if  executeBefore                  var fn   new Function executeBefore           fn            Or eventually store this in a function cache if you may need to call it multiple times    Again - don t use eval or this method if you have another way to do that

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eval   is the function you need to do that  but I d advise trying one of these things to minimize the use of eval  Hopefully one of them will make sense to you   Store the function  Store the function as a function  not as a string  and use it as a function later  Where you actually store the function is up to you   var funcForLater   clickedOnItem      later is now funcForLater t parentNode id     or  someObject funcForLater   clickedOnItem         later is now      someObject funcForLater  t parentNode id     Store function name  Even if you have to store the function name as a string  you can minimize complexity by doing   eval settings functionName   t parentNode id     which minimizes the amount of Javascript you have to construct and eval   Dictionary of handlers  Put all of the action functions you might need into an object  and call them dictionary-style using the string      global itemActions     click  clickedOnItem  rightClick  rightClickedOnItem    etc           Later    var actionName    click      Or wherever you got the action name var actionToDo   itemActions actionName   actionToDo t parentNode id      Minor note  If instead here you used syntax itemActions actionName  t parentNode id   then the function would be called as a method of itemActions

[javascript] How to turn a String into a JavaScript function call?

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