using _this=this to emulate arrow functions is fast but error-prone, requiring non-trivial analysis for use in transpilers. using .bind to emulate arrow functions is simpler, but slow in current engines. using an apply-based partial polyfill (bind) for .bind is fast in v8, slow in other engines.

bind-for-arrows.html

// <script>

/* sample output
$ node ../bind-for-arrows.html
_this: 4ms
.bind: 25ms
bind: 4ms
_this, calls only: 1ms
.bind, calls only: 4ms
bind, calls only: 0ms
.bind, inline: 22ms
.call, inline: 0ms
.apply, inline: 4ms
20000 20000 20000 30000
*/

var obj1 = {
  f: function () {
       var _this = this;
       return function (inc) {
         _this.count+=inc;
       }
     },
  count: 0
  };

var obj2 = {
  f: function () {
       return function (inc) {
         this.count+=inc;
       }.bind(this);
     },
  count: 0
  };

var obj3 = {
  f: function () {
       return function (inc) {
         this.count+=inc;
       };
     },
  count: 0
  };

function bind(f,obj) {
  return function() {
    return f.apply(obj,arguments);
  }
}

var obj4 = {
  f: function () {
       return bind(function (inc) {
         this.count+=inc;
       },this);
     },
  count: 0
  };

console.time('_this');
for (i=0; i<10000; i++) obj1.f()(1);
console.timeEnd('_this');

console.time('.bind');
for (i=0; i<10000; i++) obj2.f()(1);
console.timeEnd('.bind');

console.time('bind');
for (i=0; i<10000; i++) obj4.f()(1);
console.timeEnd('bind');

var g1 = obj1.f();
console.time('_this, calls only');
for (i=0; i<10000; i++) g1(1);
console.timeEnd('_this, calls only');

var g2 = obj2.f();
console.time('.bind, calls only');
for (i=0; i<10000; i++) g2(1);
console.timeEnd('.bind, calls only');

var g4 = obj4.f();
console.time('bind, calls only');
for (i=0; i<10000; i++) g4(1);
console.timeEnd('bind, calls only');

console.time('.bind, inline');
for (i=0; i<10000; i++) obj3.f().bind(obj3)(1);
console.timeEnd('.bind, inline');

console.time('.call, inline');
for (i=0; i<10000; i++) obj3.f().call(obj3,1);
console.timeEnd('.call, inline');

console.time('.apply, inline');
for (i=0; i<10000; i++) obj3.f().apply(obj3,[1]);
console.timeEnd('.apply, inline');

console.log(obj1.count,obj2.count,obj4.count,obj3.count);

// </script>