javascript - Referring to object properties during declaration? -

so have object, , wondering how refer other properties while declaring:

var chatter = function(io){     this.base_url = "http://chat.chatter.com:1337";     this.debug_on = true;     this.socket = io.connect(this.base_url);     this.socket.on('acknowledge', this.acknowledge); } chatter.prototype.debug = function(msg){     if(this.debug_on){         var m = {timestamp:date.create().format('{yyyy}-{mm}-{dd} {24hr}:{mm}:{ss}{tt}'), message:msg};         console.debug('#[ chatter debug ]# - {timestamp} - {message}'.assign(m));     } } chatter.prototype.acknowledge = function(data){     this.debug('acknowledgement received!'); //this throws error, claims #debug not there     this.uuid = data.uuid; }; 

calling this.debug() fails on line 5, calling this.acknowledge works. can tell me doing wrong?

the problem not chatter.prototype.acknowledge (see http://jsfiddle.net/aedvh/ )

it's way you're calling it.

this.socket.on('acknowledge', this.acknowledge); 

calls acknowledge value of this in socket callback (see this guide).

you need bind value of this context. try using .bind:

this.socket.on('acknowledge', this.acknowledge.bind(this)); 

if need support older browsers ie8, or don't bind, can manually such

   var = this;    this.socket.on('acknowledge', function(data){        that.acknowledge(data);    });