Javascript: Is there a way to use a string as a callback without eval()?

Question

So I need to make make a callback in one of my functions, but due to the way the whole program is working, I need to pass the callback function name in the form of a string rather than the function itself.

For example:

function doThings(callback){
    alert('hello');
    eval(callback + '();');
}

function test(){
    alert('world!');
}

var func = 'test';

doThings(func);

In short, I'm trying to dynamically change which function is used, and I have to use a string to represent the callback function rather than an actual function reference.

I keep reading eval is evil - is there any way to do this without eval() ?

EDIT: I do not have the ability to list out the functions in an object beforehand. I also need to pass an array as individual arguments to this function, and for some reason .apply() doesn't get along well with window[callback]()

Answer 1

Store the functions in an object. Use the property names to access them.

 function doThings(callback) { alert('hello'); my_possible_functions[callback](); } function test() { alert('world!'); } var my_possible_functions = {}; my_possible_functions.test = test; var func = 'test'; doThings(func); 

Answer 2

You can do this, in this way.

 function doThings(callback){ alert('hello'); window[callback](); } function test(){ alert('world!'); } var func = 'test'; doThings(func); 

Or you can pass the full function in string and use the Function constructor.

 function doThings(callback){ alert('hello'); (new Function('return '+callback)())(); } function test(){ alert('world!'); } var func = test.toString(); doThings(func); 

Answer 3

A very similar answer to @ Quentin 's but with additional checks

• Check if its a part of current Object
• Check if value is of type function . If value is not a function, it will break your code.

 function doThings(callback) { console.log('hello ', callback); try { callbackList[callback]() } catch (ex) { console.log(ex.message) } callbackList.hasOwnProperty(callback) && typeof(callbackList[callback]) === 'function' && callbackList[callback]() } Object.prototype.test3 = function() { console.log("this should not be called"); } var callbackList = { test: function test() { console.log('world!'); }, test2: "World" } doThings('test'); doThings("test2"); doThings("test3");