Question

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

Let’s consider I have an object:

var o = { x:1, y:2 };

What is the difference when I access a property like this:

o.x

Compared to this:

o["x"]

Answer 1

Those are called Member Operators, and there is a good bit of information on them in that link.

The only real differences are that the bracket notation allows you to disobey variable naming rules and do things like:

o["3213adascas        #@%!"] = 5;

While the following is obviously a syntax error:

o.3213adascas        #@%! = 5;

Also since bracket notation takes in a string you can use variables with it:

var o = { x:1, y:2 };
var member = 'y';
console.log(o[member]); // Outputs 2