How to Call a Dynamically-Named Method in JavaScript

How do I call a dynamically-named method in Javascript?

Assuming the populate_Colours method is in the global namespace, you may use the following code, which exploits both that all object properties may be accessed as though the object were an associative array, and that all global objects are actually properties of the window host object.

var method_name = "Colours";
var method_prefix = "populate_";

// Call function:
window[method_prefix + method_name](arg1, arg2);

How to call a function using a dynamic name in JS

Usually we should avoid eval. What you are trying to do is possible without using eval too and with a simpler code :

//variables
var ta = 3213;
var da = 44;
var s = [];

//Create string representation of function
s[1] = function test0(){  alert(" + da + "); };
s[0] = function test1(){  alert(" + ta +"); };

s.forEach((fun) => { this[fun.name] = fun;});

// calling the function
this["test"+1]();

Or simple in your code do :

this["test"+1]();

EDIT:

If you are using string and eval just because you are getting function name as string, instead you can create an object :

var data = {};
for(var i = 0; i<10; i++) {
  data['key'+ i] = function (i) { alert(i); }.bind(null, i);
}

Dynamic function name in javascript?

As others mentioned, this is not the fastest nor most recommended solution. Marcosc's solution below is the way to go.

You can use eval:

var code = "this.f = function " + instance + "() {...}";
eval(code);

How do I call a dynamically-named method with for in Javascript

If the functions are globally accessible you may write

window['a'+i]()

Otherwise, you may be able to rewrite your code to add all the functions to one variable:

var f = {
    a1: function() { },
    a2: function() { },
    a3: function() { }
};

... and call f['a'+i]().

If you're rewriting, since all functions are named by an index, you might as well write:

var myFunctions = [
  function() { },
  function() { },
  function() { }
];

... and call myFunctions[i](). (Of course, as Felix Kling points out in comments, i here would have to be adjusted to be 0-based).

Javascript Dynamic Function Call with Name

Since you want to call functions using bracket notation in object scope, not window scope, you can use this instead of window:

function meth_4()
{
    this["meth_1"]();
    this["meth_2"]();
    this["meth_3"]();
}

Dynamic function names in JavaScript

Updated answer in 2016:

The "However, that's changing..." part of the original answer below has changed. ES2015 ("ES6") was released a year ago, and JavaScript engines are now finally coming into compliance with one of its lesser-known aspects: Function#name.

As of ES2015, this function has a name despite being created using an "anonymous" function expression:

var f = function() { };

Its name is f. This is dictated by the specification (or the new one for ES2016) in dozens of different places (search for where SetFunctionName is used). In this particular case, it's because it gets the name of the variable it's being assigned to. (I've used var there instead of the new let to avoid giving the impression that this is a feature of let. It isn't. But as this is ES2015, I'll use let from now on...)

Now, you may be thinking "That doesn't help me, because the f is hardcoded," but stick with me.

This function also has the name f:

let obj = {
    f: function() { }
};

It gets the name of the property it's being assigned to (f). And that's where another handy feature of ES2015 comes into effect: Computed property names in object initializers. Instead of giving the name f literally, we can use a computed property name:

let functionName = "f";
let obj = {
    [functionName]: function() { }
};

Computed property name syntax evaluates the expression in the [] and then uses the result as the property name. And since the function gets a true name from the property it's being assigned to, voilà, we can create a function with a runtime-determined name.

If we don't want the object for anything, we don't need to keep it:

let functionName = "f";
let f = ({
    [functionName]: function() { }
})[functionName];

That creates the object with the function on it, then grabs the function from the object and throws the object away.

Of course, if you want to use lexical this, it could be an arrow function instead:

let functionName = "f";
let f = ({
    [functionName]: () => { }
})[functionName];

Here's an example, which works on Chrome 51 and later but not on many others yet:

// Get the namelet functionName = prompt(  "What name for the function?",  "func" + Math.floor(Math.random() * 10000));
// Create the functionlet f = ({    [functionName]: function() { }})[functionName];
// Check the nameif (f.name !== functionName) {    console.log("This browser's JavaScript engine doesn't fully support ES2015 yet.");} else {    console.log("The function's name is: " + f.name);}

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