Arrow function context in node.js

Question

Using the following example from the MDN documentation for Arrow functions, at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

function Person(){
  this.age = 0;

  setInterval(() => {
    this.age++; // |this| properly refers to the person object
  }, 1000);
}

var p = new Person();

When I copy/paste that code into node.js 0.12 node --harmony, the this.age++; line doesn't seem to be referring to Person context, but rather the setInterval context. Adding console.log(this) to the callback seems to confirm that.

When I've used other es6->es5 transpilers, it has always worked as expected. Is this a bug in node.js? Am I missing something?

edit: perhaps this is the reason? ES6 arrow function lexical this in V8

Difference is, they're discussing Chrome while this question is about Node.js. According to http://kangax.github.io/compat-table/es6/#arrow_functions they have different levels of ES6 support even though they both use V8.

Sure looks like you've found the reason. That question was from just under a month ago. — JLRishe
– JLRishe, Commented Feb 20, 2015 at 21:43
as @JLRishe noted, if you've found a solution you should post an answer to this question and accept it. — Nick Tomlin
– Nick Tomlin, Commented Feb 21, 2015 at 0:17
Just posted the answer, but I was hoping someone else could confirm before I did that. — az_
– az_, Commented Feb 21, 2015 at 0:54

az_ · Accepted Answer · 2015-02-21 00:55:18Z

2

Seems like the reason is that V8 has not updated to support lexical this yet.

answered Feb 21, 2015 at 0:55

az_

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