Call a JavaScript function name using a string? - Stack Overflow

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How can I hook up an event to a function name I have defined as a string?

I'm using Prototype.js, although this is not Prototype-speficic.

$(inputId).observe('click', formData.fields[x].onclick);

This would result in JavaScript complaining that my handler is not a function. I would prefer not us use eval().

How can I hook up an event to a function name I have defined as a string?

I'm using Prototype.js, although this is not Prototype-speficic.

$(inputId).observe('click', formData.fields[x].onclick);

This would result in JavaScript complaining that my handler is not a function. I would prefer not us use eval().

• javascript

Share Improve this question Follow edited Apr 6, 2012 at 5:27 user166390 asked Jan 30, 2009 at 19:50 Diodeus - James MacFarlaneDiodeus - James MacFarlane 114k3333 gold badges163163 silver badges180180 bronze badges 1

• possible duplicate of How to execute a JavaScript function when I have its name as a string – oHo Commented Nov 8, 2013 at 10:15

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10 Answers 10

Sorted by: Reset to default 94

Property accessors can be used to access any object's properties or functions.

If the function is in the global scope, you can get it using the window object:

var myFunc = window[myFuncName];

This also works within the this scope:

var myFunc = this[myFuncName];

I have worked on this problem, as I needed a function like this. Here is my sandbox code, not thoroughly tested, but can be a startpoint for others. Note that there is one eval() in the code as I couldn't figure out how to bypass that step, maybe a javascript quirk and cannot be done in any other way. Let me know if there is a way to get rid of eval() here!

executeFunctionByName = function(functionName)
{
    var args = Array.prototype.slice.call(arguments).splice(1);
    //debug
    console.log('args:', args);

    var namespaces = functionName.split(".");
    //debug
    console.log('namespaces:', namespaces);

    var func = namespaces.pop();
    //debug
    console.log('func:', func);

    ns = namespaces.join('.');
    //debug
    console.log('namespace:', ns);

    if(ns == '')
    {
        ns = 'window';
    }

    ns = eval(ns);
    //debug
    console.log('evaled namespace:', ns);

    return ns[func].apply(ns, args);
}


core = {
    paragraph: {
        titlebar: {
            user: "ddd",
            getUser: function(name)
            {
                this.user = name;
                return this.user;
            }
        }
    }
}

var testf = function()
{
    alert('dkdkdkd');
}

var x = executeFunctionByName('core.paragraph.titlebar.getUser', 'Ikon');
executeFunctionByName('testf');

... or this[myFuncName];

Perhaps?

setTimeout ( "myFunc()", 1 );

Just an eval would do the job

var call = eval("method_name").call(args);

Looks like formData.fields[x].onclick holds the name of a global function? If so try:

$(inputId).observe('click', window[formData.fields[x].onclick]);

window.myFunction === window["myFunction"]

Do you know what the onclick property contains or what type it is? I assume this is prototype specific stuff, as "fields" does not exist in DOM forms.

update:--- use ES6 export and import

a.js

const fn = {
  aaa: function() {
    //code
  },
  bbb: function() {
    //code
  },
  //codes ....
  nnn: function() {
    //code
  }
}

export default fn

b.js

  import someFn from './a'
  //eg
  const str1='aaa'
  const str2 = 'bbb'

  someFn[str1]()

---

• eval('str') (obsolete feature https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features )

• setTimeout('str') setInterval('str')

• window['str'] (but...sometimes,global object is not window)

• new Function('str')

These methods above always not be recommend by some reasons, but they are really convenient to use. These methods below are safe, but really not conveninet to use.

• switch...case (or if...else)

  switch(str){
      case 'str1': 
          fn1()
          break
      case 'str2':
          fn2
          //and so on
  }
  

• put functions in a object

  const fn={
      str1:fn1,
      str2:fn2
      //and so on
  }
  fn[str1] //call function
  

If you need to call a string function with arguments, do this:

window[stringFunctionName].apply( window, arrayOfArguments )

You can use scope in place of window if preferred

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