Question

I am trying to get a better understanding of the jQuery.map function.

So in general terms .map takes a array and ‘maps’ it to another array of items.

easy example:

$.map([0,1,2], function(n){     return n+4; }); 

results in [4,5,6]

I think I understand what it does. I want to under why would someone need it. What is the practical use of this function? How are you using this in your code?

Answer 1

$.map is all about converting items in a set.

As far as the DOM, I often use it to quickly pluck out values from my elements:

var usernames = $('#user-list li label').map(function() {     return this.innerHTML; }) 

The above converts the <label> elements inside a list of users to just the text contained therein. Then I can do:

alert('The following users are still logged in: ' + usernames.join(', '));