How to use hashmap in javascript

I have a hash map I want to use it in javascript. So I thought of converting it in开发者_StackOverflow社区to javascript map..how to use it or to do?

Turn it into an object literal...

var map = {
   'a' : 'a',
   'b': 'b'
   ...
};

Or use Associative Arrays, for example:

var arr = new Array();
arr["One"] = 1;
arr["Two"] = 2;
arr["Thr"] = 3;
arr["For"] = 4;

for(var i in arr)
{
    alert('Key='+i + ', Value = '+arr[i]);     
}