Alternative to .on('error', this.onError.bind(this)) in ES6?

Question

function Person()
}

function Person.prototype.init() {   
  request('http://google.fr').on('error', this.onError.bind(this));
}

function Person.prototype.onError(error) {
  console.log(error);
}

bind.this is in init() required. What ECMAScript 6 alternatives do I have here to deal with this? Is this the only solution, doesn't seem that I can apply the arrow here.

Can you please fix your syntax errors? You cannot use dots in a function identifier. — Bergi, Sep 26 '15 at 13:37
Why are you binding this method at all? It looks rather static to me. — Bergi, Sep 26 '15 at 13:38
possible duplicate of [can i use ES6 fat arrow in class methods?](http://stackoverflow.com/q/31362292/1048572) — Bergi, Sep 26 '15 at 14:43
@Bergi Stripped down my example, my actual code access the state of Person. — Mahoni, Sep 26 '15 at 16:27

sdgluck · Accepted Answer · 2015-09-26T13:54:05.497

To answer your question directly, ES6 doesn't offer any additional functionality that we can use to avoid binding onError at its point of invocation. ES6 hasn't done away with the behaviour of JavaScript's execution context.

As a side note, the way that you are declaring your instance methods is illegal and will throw an error. They should be declared as follows:

Person.prototype.init = function () {   
    request('http://google.fr').on('error', this.onError.bind(this));
};

Person.prototype.onError = function (error) {
    console.log(error);
};

Currently your onError method will not suffer from any errors if passed unbound. This is because you don't use this inside the onError method's body:

// Safe unbound method
Person.prototype.onError = function (error) {
    console.log(error);
};

// Unsafe unbound method
Person.prototype.onError = function (error) {
    console.log(this, error);
             // ^^^^
};

score 1 · Answer 2 · answered Sep 26 '15 at 13:14

1

You can use fat arrow functions:

request('http://google.fr').on('error', (error) => this.onError(error));

answered Sep 26 '15 at 13:14

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Not sure if this is an improvement. – Mahoni Sep 26 '15 at 13:29

Alternative to .on('error', this.onError.bind(this)) in ES6?

2 Answers2