Question

Say I have an object:

var myObj = function {
this.count = 0;
}

myObj.prototype {
   setCount : function() {
       var interval = setInterval(function() {
           this.count++;
       }, 500);
   }
}

The issue is count is always undefined within the setInterval so i can never increment the count variable within myObj to be something other than 0.

Answer 1

this changes depending on the function being called (and how it said function is called).

The anonymous function you pass to setInterval is a different function.

Copy the value to a non-magic variable first.

   setCount : function() {
       var that = this;
       var interval = setInterval(function() {
           that.count++;
       }, 500);

See the this problem in the documentation.