Add the below code in your js.

// Defines push method to push the key value pair
Object.prototype.push = function( key, value )
        this[ key ] = value;
        return this;
// Declare variable for map;

var obj2 = ;
obj2 = "key1": "value1", "key2": "value2"; // a way of adding map data.
obj2.push( "key3", "value3" );

console.log ( obj2 ["key2"] ); // Prints: value2

console.log ( obj2 ); 
// Prints: key1: "value1", key2: "value2", key3: "value3"

Thats all you can construct the data structure as you wish.