Implement Java Map in Javascript

//Map is an Object Literal 
var map = {};

//Key Needs To be a String
var key = "";

// Value can be any String, Number or an Object itself
var value;

//------- Method I --------------

// Assign a value to a key 
map[key] = value;

// Return value by a key 
var returnedValue = map[key];

//-------- Method II ----------

// Return value by a key
var returnedValue = map.key;

// Assign a value to a key
map.key = value;