unobtrusive rollover coffeescript vs original

unobtrusive_rollover.js

// purpose of script is to handle rollovers unobtrusively, e.g.
// <img src='original.png' data-rollover='rolled.png'>

$(function(){
  $('img[data-rollover]').live('mouseover', function(){
    if($(this).data('rollover-original') == null) {
      $(this).data('rollover-original', $(this).attr('src'))
    }
    $(this).attr('src', $(this).data('rollover'))
  }).live('mouseout', function(){
    $(this).attr('src', $(this).data('rollover-original'))
  })
})

unobtrusive_rollover.js.coffee

# coffeescript version
# eh, it's not that much nicer. Maybe if I could replace '$(this)' with something like '$@' ?
# but then it starts looking like perl :(
$ ->
  $('img[data-rollover]').live 'mouseover', ->
    $(this).data 'rollover-original', $(this).attr('src') unless $(this).data('rollover-original')?
    $(this).attr 'src', $(this).data('rollover')
  .live 'mouseout', -> $(this).attr 'src', $(this).data('rollover-original')

Yeah, jQuery code tends to benefit only minimally from being converted to CoffeeScript. I'd actually add a little more punctuation than you used, e.g.:

$ ->
  $('img[data-rollover]')
    .live('mouseover', ->
      $this = $(this)
      unless $this.data('rollover-original')?
        $this.data 'rollover-original', $this.attr('src')
      $this.attr 'src', $this.data('rollover')
    ).live('mouseout', ->
      $this = $(this)
      $this.attr 'src', $this.data('rollover-original')
    )

(The $this = $(this) is pretty standard; there's a bit of overhead every time you use the $ function, plus the parentheses hurt readability.) Relying less on implicit parentheses makes it easier to extend the code in the future.

Also, be carefuly about implicit returns. It's not an issue in this case ($this.attr() will just return $this), but if you were to accidentally return false from an event handler, that would stop the event from propagating, and possibly have other unintended consequences. So you may want to explicitly add return at the end of each callback as a matter of habit.

And thus why I'm not impressed. Most of my Javascript code is jQuery - I so rarely use, say, regular arrays, or for loops, or even 'var'. I suppose if I was doing something with insane amounts of logic on the front end - or if I start playing with node.js - it might be useful. The other thing of it is that while I hate extra brackets and like using indents - as in haml and sass - Javascript is sort of Lisp in sheep's clothing. I finally understood my Lisp classes once I understood Javascript... so I don't mind the brackets as much, I guess I figure they're no worse, and maybe a little better than ))))))))))))))) like at the end of a long Lisp expression. Past that, I've had enough trouble with people balking at haml because 'designers know html.' I had one client convert all my haml back to erb after I finished a project. Grrr. I'm not sure if I'd ever trust a 'designer' to play with my templates too much anyway... but I can see a case where I might want to have someone else working on js and can see it being an issue. Coffeescript is nice, don't get me wrong, it's a heroic effort, and I thank you very much for your attention! You've done a really nice job! :) :) but I think I'll stick with mostly plain old js/jquery, and maybe use Coffeescript if I need to do something fancy. Thank heavens for Sprockets making that easy finally. Keep up the good work, and thanks again!

…

On Sat, Jun 4, 2011 at 1:35 PM, TrevorBurnham < ***@***.***>wrote: Yeah, jQuery code tends to benefit only minimally from being converted to CoffeeScript. I'd actually add a little more punctuation than you used, e.g.: $ -> $('img[data-rollover]') .live('mouseover', -> $this = $(this) unless $this.data('rollover-original')? $this.data 'rollover-original', $this.attr('src') $this.attr 'src', $this.data('rollover') ).live('mouseout', -> $this = $(this) $this.attr 'src', $this.data('rollover-original') ) (The `$this = $(this)` is pretty standard; there's a bit of overhead every time you use the `$` function, plus the parentheses hurt readability.) Relying less on implicit parentheses makes it easier to extend the code in the future. Also, be carefuly about implicit returns. It's not an issue in this case (`$this.attr()` will just return `$this`), but if you were to accidentally return `false` from an event handler, that would stop the event from propagating, and possibly have other unintended consequences. So you may want to explicitly add `return` at the end of each callback as a matter of habit.

Hey, if you'd rather type function() { } instead of ->, be my guest. :)

I think where CoffeeScript really shines is in large applications, where classes provide a very neat way of organizing your code (even if you're not totally into classical OO). I hope you'll keep that in mind in your front-end coding endeavors.

On Sat, Jun 4, 2011 at 4:52 PM, TrevorBurnham < ***@***.***>wrote: Hey, if you'd rather type `function() { }` instead of `->`, be my guest. :)

Actually in Textmate I just have to do f-tab, so it's actually less keystrokes. In fact, I had actually forgotten about this shortcut and had been typing it manually until I saw your comment and I was like "oh, right, there's a shortcut for that!" I agree in principle though, and yes -> looks nicer, and yes it's more expressive.

I think where CoffeeScript really shines is in large applications, where classes provide a very neat way of organizing your code (even if you're not totally into classical OO). I hope you'll keep that in mind in your front-end coding endeavors.

Sure, and I have to say, I don't do a lot of real object oriented JS, I don't generally make my own, umm, what do they call them? prototypes or something? I don't really do my own libraries, and I really ought to, and I see where this might make those a lot cleaner.

It is worth noting that I am now a coffeescript convert - today I would no sooner use plain JS instead of coffeescript than I would use html or erb instead of haml or slim.