Assistance with JavaScript snippet not working. old deprecated practices

Question

Important: this question was posted in 2010, it's no longer relevant as JS practices evolved since then. This platform unfortunately doesn't allow deletion.

I will put my code in a simple way, but if any good soul wants to help the code is |on Github| /lib/inmotion/editor.js(line 99)

editor.js

function Editor(){
  var instance = this;
  this.key_frames = [] // a list of key frames
  this.kf = null   // the current KeyFrame

  function notice_click( click ){
    instance.kf.add_bone( 1 ) // <-- error here
    // instance.kf.list.push( 1 ) // <-- this works, but is incomplete
  }
}

key_frame.js

function KeyFrame(){
  instance = this
  instance.changed = false // for the redraw :)
  instance.list = []
  
  function add_bone( bone ){
    instance.list.push( bone )
    instance.changed = true
    return true
  }
}

My program has an unique Editor instance that has lots of instances of KeyFrames.
Each KeyFrame holds lots of bones.
So there is always one active KeyFrame, defined by instance of Editor.kf
As I only have one kf, I can add bones to that one with no problem, but as I add more KeyFrames I can only add_bone to the last kf I created! Why?

If I was not clear enough, I apologize, ask on doubt

First, use semicolons, yes they're sometimes optional...when you get down to it there's no legitimate excuse for not using them, use them, be explicit. Second, instance = this is setting a global variable named instance, you need var instance = this; for it to be local. — Nick Craver
– Nick Craver, Commented Jul 19, 2010 at 3:43
@Nick Craver: Yes, precisely , don't you want to make this an answer so I can chose as accepted ? — Fabiano Soriani
– Fabiano Soriani, Commented Jul 19, 2010 at 6:33

goffrie · Accepted Answer · 2010-07-19 03:48:05Z

2

The problem, as far as I understand it, is that 'instance' gets overwritten each time you call KeyFrame. You should use 'this' directly.

answered Jul 19, 2010 at 3:48

goffrie

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1 Comment

Fabiano Soriani Over a year ago

I used to think the same about the 'this', but as this guy gave a great explain here: stackoverflow.com/questions/3045953

Nick Craver · Accepted Answer · 2010-07-19 10:16:39Z

1

Your KeyFrame object is missing a var, it should look like this:

function KeyFrame(){
  var instance = this;
  instance.changed = false;
  instance.list = [];

  function add_bone( bone ){
    instance.list.push( bone );
    instance.changed = true;
    return true;
  }
}

Without the var keyword you're defining or overwriting window.instance, a global variable, not a local one to the object like you want :)

answered Jul 19, 2010 at 10:16

Nick Craver

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