If you are doing some more advanced JavaScript applications, you’ll likely run into the problem at one point or another when you need to dynamically generate the name of a function you wish to call. This is the equivalent of PHP’s call_user_func().

Here’s how you can do it.

// Define some vars
var foo = "hello";
var bar = "world";
var function_name = "say_" + foo + bar;

// Since its name is being dynamically generated, always ensure your function actually exists
if (typeof(window[function_name]) === "function")
    window[function_name](" World!");
    throw("Error.  Function " + function_name + " does not exist.");

function say_helloworld(the_word)
    alert("Hello " + the_word);

// Browser will alert "Hello World!"

When you think about it, it makes a lot of sense considering all global objects in JavaScript are actually properties of the “window” object. Take a look at this example to understand that concept a bit more.

var foo = "apple";

function foobar()
    var foo = "orange";
    alert(window["foo"]); // alerts "apple"
    alert(foo); // alerts "orange"
    alert(window["foobar"]); // alerts the foobar function


Here’s another example of when using a string to call a function could come in handy. This time we’re calling the property of an object we’ve created.

function Person()
    this.message = "Hello World!";
    this.say_hello = function(to)

var Derek = new Person();
function_name = "say_hello";

See how it looks pretty much the same as the method above using a global function?

Hope that shed some light on your problem.