Question

In my code I have the following:

var setTheme = function (color) {

};

function setTheme(color) {

};

The function names are not really the same but I have put the same here. Is there a difference in the two ways of creating a function?

Answer 1

There is a difference. With a function definition, the entire definition is hoisted:

foo(5); // Pops up 5

function foo(n) {
    alert(n);
}

Whereas with var, the declaration is hoisted but the assignment is not:

foo(5); // Error!

var foo = function(n) {
    alert(n);
};

Another difference I noticed is that on Google Chrome Canary (currently and at least, I haven’t tried in many other browsers) in ECMAScript 5 strict mode, a function definition cannot be nested more than one level deep:

!function() {
    'use strict';

    function Blah() {
        function Lol() { // Error.
        }
    }
}();