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JavaScript JavaScript Foundations Functions Anonymous Functions

Anonymous Functions Clarification

Can someone please give me another explanation of the significance or practical application of the anonymous function?

Does it have to do with scope? It seems like they're called the same way, and there doesn't seem to be a difference in how they're executed.

2 Answers

Hi Mike,

It does make handling scope easier sometimes.

I also like anonymous functions because it makes reading the JavaScript easier.

For example, in jQuery if you fade out a DOM element, you might want to do something else after it disappears, such as set a flag value to be used elsewhere in your code. Creating a named function here would be unnecessary and arguably, harder to read in a large application.

For example, I would do something like this:

var paragraphHidden = false;

$("#myParagaph").fadeOut("slow", function() {

    paragraphHidden = true;


Although the code below would also work, I wouldn't normally do this, unless I thought my function setFlag might be used elsewhere in my application:

var paragraphHidden = false;

$("#myParagaph").fadeOut("slow", setFlag());

function setFlag() {
    paragraphHidden = true;

Hi Mike,

This article explains anonymous functions a little, i.e. "Not having to set a name for an anonymous function is just a convenience thing since in most cases the name of the function doesn’t really matter. Most of the time anonymous functions and named functions will both do any job perfectly well."

I also find anonymous functions useful when creating an object that contains methods/functions inside it, to do certain things.

A great example of this can be found in John Resig's excellent book. Below I've shown a modified version of his example from the book:

function Ninja() {
    var feints = 0;

    this.getFeints = function() {
        return feints;

    this.feint = function() {


var ninja_1 = new Ninja();
var ninja_2 = new Ninja();

ninja_1.feint(); // increments the fients variable inside the Ninja object

alert(ninja_1.getFeints()); // displays the number of feints, i.e. 1 feint
alert(ninja_2.getFeints()); // displays the number of feints in our second ninja, i.e. 0 feints


Thanks Ian, your links provided the distinction I was looking for. I'll check out that book.