Question

Possible Duplicate:
Why doesn't this closure have access to the 'this' keyword? – jQuery

function class1() {
    this.url = 'http://en.wikiquote.org/w/api.php?action=query&format=json&prop=revisions&titles=Albert_Einstein&rvprop=content&callback=?';

    this.f = function() {
        $.getJSON(this.url, function() {
            console.log(this.url);
        });
    }
};

var obj = new class1();
obj.f();

Instead of printing the url, obj.f() prints “undefined” to the console. Why is this happening and what can I do to prevent this behaviour?

Answer 1

Inside your ajax callback, this will be the jqXhr object, not your current object. You’ll want to save the value of this before your ajax call, and reference that in your callback:

this.f = function() {
    var self = this;
    $.getJSON(this.url, function() {
        console.log(self.url);
    });
}