Run results for: WeakMap vs "Symbol with WeakMap fallback"

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36

Browser: Chrome 83

Operating system: Mac OS X 10.15.5

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
WeakMap get	7189347.0 Ops/sec
Symbol with WeakMap fallback get	7201821.0 Ops/sec
WeakMap set	6821954.5 Ops/sec
Symbol with WeakMap fallback set	7176508.0 Ops/sec

Script Preparation code:

var c = Symbol === undefined
? (function() {
  var x = function() {
    this._x = new WeakMap();
  }
  x.prototype.get = function(x) { return this._x.get(x); };
  x.prototype.set = function(x,y) { this._x.set(x,y); };
  return x;
})()
: (function() {
  var x = function() {
    this._x = Symbol();
  }
  x.prototype.get = function(x) { return x[this._x]; };
  x.prototype.set = function(x,y) { x[this._x] = y; };
  return x;
})();

var to0 = {};
var to1 = {};
var wm = new WeakMap();
var fwm = new c();
wm.set(to1, 1);
fwm.set(to1, 1);

Tests:

WeakMap get
let r = wm.get(to1);
Symbol with WeakMap fallback get
let r = fwm.get(to1);
WeakMap set
wm.set(to0, 1);
Symbol with WeakMap fallback set
fwm.set(to0, 1);

Run results for: WeakMap vs "Symbol with WeakMap fallback"

WeakMap get

Symbol with WeakMap fallback get

WeakMap set

Symbol with WeakMap fallback set