Javascript Nested Functions Scope

Question

I have the following javascript object, somewhat pseudocode:

{
  dateField: new Date(),
  addMinutes:function(numMinutes)
  {
     CallWebService(numMinutes, function{alert(this.dateField; });
  }
}

The problem is the scope of the callback function in CallWebService doesn't see the dateField property of the object. Is there a way I can access it? Thanks!

Answer 1

You need to preserve the context (the this value) of the addMinutes function.

There are several ways to achieve it, the most easy one is to simply store a reference of this on a variable, that variable will be available to the scope of the callback function, e.g.:

var obj = {
  dateField: new Date(),
  addMinutes: function(numMinutes) {
     var instance = this;
     CallWebService(numMinutes, function () {
       alert(instance.dateField);
     });
  }
};