Backbone.js setTimeout() loop in CoffeeScript

Question

Seems like every way I try this, it throws some sort of error. Here's what my code looks like now:

runShow: ->
  moments = @model.get('moment_stack_items')
  if inc == moments.length
    inc = 1
    pre = 0
  $("#" + moments[pre].uid).hide("slide", { direction: "left" }, 1000)
  $("#" + moments[inc].uid).show("slide", { direction: "right" }, 1000)

  inc += 1
  pre += 1

  console.log "looping" + inc
  t = setTimeout(this.runShow(),2000);

I call the function in my events. I have inc = 1 and pre = 0 defined outside the Backbone.View.. My current error is "Uncaught TypeError: Object [object DOMWindow] has no method 'runShow'"
BONUS POINTS: how can I reference t from another function (to run my clearTimeout(t))?

Using strings in your setTimeout is calling eval behind the scenes. I would strongly consider changing this to a reference of the function. e.g. t = setTimeout(this.runShow ,2000); http://stackoverflow.com/questions/86513/why-is-using-javascript-eval-function-a-bad-idea — Gazler, Aug 18 '11 at 16:43
fair enough @Gazler, I've removed it from the code. The solution by user576875 also has it removed. — pizza247, Aug 18 '11 at 16:59

Arnaud Le Blanc · Accepted Answer · 2011-08-18T16:40:46.143

8

You ask the setTimeout function to evaluate "this.runShow()", and setTimeout will do that in the context of window. This means that this is the window object when this code is evaluated.

To avoid this you can create a function and bind it to a the current context, so that everytime the function is called, this is the same as when the function has been created.

In coffee script you can do this with the =>:

func = =>
    this.runShow()

setTimeout(func, 2000)

Or on a single line:

setTimeout((=> this.runShow()), 2000)

how can I reference t from another function?

Make t a property of your object:

class Something
    t: null
    runShow: ->
       ...
       this.t = ...
    otherFunction: ->
       t = this.t

edited Aug 18 '11 at 16:40

answered Aug 18 '11 at 16:23

Arnaud Le Blanc

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Brilliant solution @user576875. Thanks for responding so quickly! I hadn't even thought to use => – pizza247 Aug 18 '11 at 16:38
I actually prefer what you had before your edit! Much more concise and looked cleaner in my backbone view. – pizza247 Aug 18 '11 at 16:41
1

You mean this syntax: `setTimeout((=> this.runShow()), 2000)` ? – Arnaud Le Blanc Aug 18 '11 at 16:42
Yea, It just looks cleaner to me. – pizza247 Aug 18 '11 at 16:49

Backbone.js setTimeout() loop in CoffeeScript

1 Answers1