Question

Possible Duplicate:
JavaScript property access: dot notation vs. brackets?

<script>      
  var foo = {          
    name: 'kevin'        
  };

  document.write(foo.name);
  document.write(foo['name']);

  var cool = 'name';
  document.write(foo.cool);

  document.write(foo[cool]);      
</script>

1. Why does foo.cool returns me undefined where as foo[cool] returns
me kevin.
2. How does cool actually refer to my name property in foo object.

Answer 1

1. A cool property is not defined on foo, so foo.cool is undefined. If you did foo.name, it would return kevin.

2. cool in foo[cool] is the one you defined in the line above it, so it is actually foo['name'], which is defined and has the value kevin.