Question

I’m trying to implement a kind of multiplayer extension to a game I’m creating. After a XMLHttpRequest, a game ID is returned, i.e. the ID of a multiplayer session.

I’m using the following code, in which Multiplayer is a static class:

var Multiplayer = {
    baseURL: 'http://127.0.0.1:8888/m',
    gameID: -1,

    create:
    function() {
        $.get(this.baseURL, {'a':'c'}, function(text) {
            this.gameID = parseInt(text);
        });
    }
}

It fails, because it seems this.gameID = parseInt(text) cannot be used. When I change it to Multiplayer.gameID = parseInt(text), it works like a charm.

It seems like this.gameID is undefined, while Multiplayer.gameID can both be written to and read from.

Is this correct and if so, why is this the case?

Answer 1

Javascript doesn’t have classes, and this does not behave as you expect coming from a C++ or Java background. Try changing your create function to this:

function() {
    var that = this;
    $.get(this.baseURL, {'a':'c'}, function(text) {
        that.gameID = parseInt(text);
    });
}

The key points are that every function() is invoked with a particular this value, and it may not be the same value as the enclosing function’s.