How to change the context of a function in javascript

Question

I\'m trying to understand why in javascript, you might want to change the context of a function. I\'m looking for a real world example or something which will help me unders

Answer 1

It's very useful when doing callbacks from AJAX requests:

function Person(_id, _name) {
    this.id = _id;
    this.name = _name;
};

Person.prototype.sayHi = function(greeting) {
    alert(greeting + " from " + this.name);
};

Person.prototype.loadFromAJAX = function(callback) {
    // in this example, it's jQuery, but could be anything
    var t = this;
    $.get("myurl.php", function(data) {
        callback.call(t, data.greeting);
    });
};

Actually, that's a pretty crappy example.

There are tons of uses of it in jQuery. For example, the jQuery().get() function:

get: function( num ) {
    return num === undefined ?
        // Return a 'clean' array
        Array.prototype.slice.call( this ) :
        // Return just the object
        this[ num ];
}

It's using the functions of the Array prototype but in the context of the jQuery object.