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BTW, imo, the behavior of |this| is a really unfortunate design flaw of JS. The amount of time that must have been spent learning and teaching this edge case ov

BTW, imo, the behavior of |this| is a really unfortunate design flaw of JS. The amount of time that must have been spent learning and teaching this edge case over and over to every person new to the language is ... well, it's big.

Bluem00 17y ago
Do you know why it was designed this way? Was 'new' added to javascript after the behavior of 'this' was already well defined and the creators did not feel comfortable changing it?
- jmtulloss 17y ago
  actually, no. As I understand it, the language was supposed to be some sort of weird conglomeration between traditional object oriented languages and dynamic, lisp-ish languages. The problem was that the creators had about 30 seconds to get this done and they could make things look more "normal" by not explicitly supporting every feature they envisioned. "new", I believe, is actually an ancient relic of the prototypal class system. That's another topic entirely, but it's incredibly cool. Check out Douglas Crockford's articles on inheritance if you want closure on the issue. He has written way more than I have on the topic.
  - praptak 17y ago
    "new", I believe, is actually an ancient relic of the prototypal class system. I believe it is quite the opposite. It was a failed attempt to make the prototype-based object system look like class-based one. I vaguely remember reading this opinion in Crockford's "Javascript:The Good Parts" book.
    - jmtulloss 17y ago
      Agreed. That's actually what I was trying to say. It's an ancient relic of JavaScript's implementation of the class system.
vicaya 17y ago
The behavior of 'this' is from DOM bindings and not from the language per se. Javascript can set 'this' of any calling context to any object with 'apply' or 'call'. The convention for on* handlers is that 'this' is set to the DOM element when the handlers are called. I only learned to appreciate this, when I wrote my own little JS DOM framework a la JQuery or Dojo.
- litewulf 17y ago
  I believe actually that 'this' points to the global object. So if there is no obvious thing for this to point at, it'll point at the global object. Its just implementation detail that in browsers it points to the window object.

Bluem00 17y ago

Do you know why it was designed this way? Was 'new' added to javascript after the behavior of 'this' was already well defined and the creators did not feel comfortable changing it?

jmtulloss 17y ago
actually, no. As I understand it, the language was supposed to be some sort of weird conglomeration between traditional object oriented languages and dynamic, lisp-ish languages. The problem was that the creators had about 30 seconds to get this done and they could make things look more "normal" by not explicitly supporting every feature they envisioned. "new", I believe, is actually an ancient relic of the prototypal class system. That's another topic entirely, but it's incredibly cool. Check out Douglas Crockford's articles on inheritance if you want closure on the issue. He has written way more than I have on the topic.
- praptak 17y ago
  "new", I believe, is actually an ancient relic of the prototypal class system. I believe it is quite the opposite. It was a failed attempt to make the prototype-based object system look like class-based one. I vaguely remember reading this opinion in Crockford's "Javascript:The Good Parts" book.
  - jmtulloss 17y ago
    Agreed. That's actually what I was trying to say. It's an ancient relic of JavaScript's implementation of the class system.

vicaya 17y ago

The behavior of 'this' is from DOM bindings and not from the language per se. Javascript can set 'this' of any calling context to any object with 'apply' or 'call'. The convention for on* handlers is that 'this' is set to the DOM element when the handlers are called. I only learned to appreciate this, when I wrote my own little JS DOM framework a la JQuery or Dojo.

litewulf 17y ago
I believe actually that 'this' points to the global object. So if there is no obvious thing for this to point at, it'll point at the global object. Its just implementation detail that in browsers it points to the window object.