Calling a JavaScript function named in a variable

Question

I have a JavaScript variable which contains the name of a JavaScript function  This function exists on the page by having been loaded in and placed using   ajax  etc   Can anyone tell me how I would call the javascript function named in the variable  please   The name of the function is in a variable because the URL used to load the page fragment  which gets inserted into the current page  contains the name of the function to call   I am open to other suggestions on how to implement this solution

User · Accepted Answer

I d avoid eval   To solve this problem  you should know these things about JavaScript    Functions are first-class objects  so they can be properties of an object  in which case they are called methods  or even elements of arrays  If you aren t choosing the object a function belongs to  it belongs to the global scope  In the browser  that means you re hanging it on the object named  window   which is where globals live  Arrays and objects are intimately related   Rumor is they might even be the result of incest   You can often substitute using a dot   rather than square brackets     or vice versa    Your problem is a result of considering the dot manner of reference rather than the square bracket manner   So  why not something like   window  functionName        That s assuming your function lives in the global space  If you ve namespaced  then   myNameSpace  functionName        Avoid eval  and avoid passing a string in to setTimeout and setInterval  I write a lot of JS  and I NEVER need eval   Needing  eval comes from not knowing the language deeply enough  You need to learn about scoping  context  and syntax  If you re ever stuck with an eval  just ask--you ll learn quickly

User · Answer

If it  s in the global scope it  s better to use   function foo         alert  foo       var a    foo   window a       than eval    Because eval   is evaaaaaal   Exactly like Nosredna said 40 seconds before me that is    lt

User · Answer

Definitely avoid using eval to do something like this  or you will open yourself to XSS  Cross-Site Scripting  vulnerabilities   For example  if you were to use the eval solutions proposed here  a nefarious user could send a link to their victim that looked like this   http   yoursite com foo html func function   alert  Im 20In 20Teh 20Codez      And their javascript  not yours  would get executed   This code could do something far worse than just pop up an alert of course  it could steal cookies  send requests to your application  etc   So  make sure you never eval untrusted code that comes in from user input  and anything on the query string id considered user input    You could take user input as a key that will point to your function  but make sure that you don t execute anything if the string given doesn t match a key in your object   For example      set up the possible functions  var myFuncs       func1  function      alert  Function 1         func2  function      alert  Function 2         func3  function      alert  Function 3         func4  function      alert  Function 4         func5  function      alert  Function 5            execute the one specified in the  funcToRun  variable  myFuncs funcToRun       This will fail if the funcToRun variable doesn t point to anything in the myFuncs object  but it won t execute any code

User · Answer

This is kinda ugly  but its the first thing that popped in my head   This also should allow you to pass in arguments   eval  var myfunc       variable    myfunc args          If you don t need to pass in arguments this might be simpler   eval variable             Standard dry-code warning applies

[javascript] Calling a JavaScript function named in a variable

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