Native WeakMap vs es6-weak-map

gistfile1.js

var NativeWeakMap = WeakMap;

global.WeakMap = null;

var PolyWeakMap = require('es6-weak-map');

var itterations = 1000000,
    key = {};

var nativeWM = new NativeWeakMap();
nativeWM.set(key, 1);
    
var start = Date.now();
for(var i = 0; i < itterations; i++){
    nativeWM.get(key);
}
console.log(Date.now() - start);


var polyWM = new PolyWeakMap();
polyWM.set(key, 1);
    
var start = Date.now();
for(var i = 0; i < itterations; i++){
    polyWM.get(key);
}
console.log(Date.now() - start);

On my pc:

Native: 140
Poly: 307

Poly is faster than native for small iterations though (1000):

Native: 7
Poly: 1

Massive iterations (10000000):

Native: 1203
Poly: 3496

The above results are for io.js

In chrome 43.0.2357.125 (64-bit), the polyfill is always slower:

1000:
Native: 1,
Poly: 2

100000:
Native: 17,
Poly: 46

10000000:
Native: 1068,
Poly: 4205