In Javascript, under what conditions is it appropriate to only use `this` in constructor functions?

Question

I found an interesting line of code in JSHint's config options.

The comment associated with the option reads Tolerate using this in a non-constructor function.

I am confused. Am I misunderstanding the config option?

Aren't there a lot of cases where you want to use this in a non-constructor function? When would you ever want to be warned about it?

Check this out:- http://www.phpied.com/3-ways-to-define-a-javascript-class/ — Rahul Tripathi, Aug 15 '13 at 15:15

score 1 · Accepted Answer · answered Aug 15 '13 at 15:14

This options is used to tell JSHint that a function will be invoked with a valid this parameter.

For example:

function myRandomFunction() {
    alert(this.something);
}

myRandomFunction.call(someObject);

If strict mode is on, JSHint will warn that myRandomFunction shouldn't be using this, since it doesn't look like a constructor or a member function.
If you know that it will always be called with a this (eg, as a callback), you can add /*jshint validthis: true */ to suppress the warning.

This makes good sense. I guess the config option just needed a little bit more context :) — Cho Naseo, Aug 15 '13 at 16:00

score -1 · Answer 2 · answered Aug 15 '13 at 15:19

-1

I think that every "this" on a non-constructor function could be replaced with a meaningful parameter. On the other hand, badly implemented functions that use the "this" referenced object can easily mess up the application with hard-to-debug errors. So, I really think it's a valid option, specially if project team is large and some members aren't very experienced.

answered Aug 15 '13 at 15:19

samuelgrigolato

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The statements `duck.quack()` and `quack(duck)` are completely different. – Esailija Aug 15 '13 at 15:40
Fair enough.. While writing my answer I was thinking about functions, that aren't class members, messing up with the current scope.. – samuelgrigolato Aug 15 '13 at 16:29

In Javascript, under what conditions is it appropriate to only use `this` in constructor functions?

2 Answers2