As much as I try, I cannot seem to get this Coffeescript code to look beautiful (I'd like to think it is possible). I have tried both Javascript and Coffeescript. Just to be clear, this code works fine, but it is hard to read, for reasons that I am unable to pinpoint.

How can it be refactored, reorganized, and what changes to coding style can be made to make it more appealing to read?

define [
], (ui, highlight) ->
  editor = {}

  jQuery ($) ->
    # A widget to view source code.
    $.widget 'core.editor',
      _create: ->
        $editor = $(this.element)
          .append($('<ul spellcheck="false" contenteditable> <li></li> </ul>'))

        # Move the gutter along with the editable area.
        this.lines().bind 'scroll', (event) ->
          $this = $(this)
          $this.siblings(".gutter").css(top: $this.scrollTop() * -1)

      # Highlight the sourceview using the given language.
      # The language's JSON rule file is loaded.
      highlight: (language) ->
        this.language = language
        require ["text!plugins/editor/js/#{ language }.json"], (json) =>
          this._rules = JSON.parse(json)

      # Update the `left` of the `<ul>` based on the gutter width.
      # Each time the number of digits in the gutter changes, it becomes wider or
      # narrower, and the editor needs the shift accordingly.
      updateGutterWidth: () ->
        # The `8` is the gutter's left padding.
        this.lines().css(left: this.gutter().width() + 8)

      # Add or remove line numbers if the number of lines has changed.
      # `change` is a modification the the line count (In case the character was not yet
      # typed).
      updateLineNumbers: (change = 0) ->
        $gutter = this.gutter()
        count =   this.lines().children("li").length
        current = $gutter.children("span").length

        count += change

        # Add lines
        if (count > current)
          for i in [current..(count - 1)]
            ele = document.createElement("span")
            ele.innerText = "#{ i + 1 }"
        # Remove lines
        else if (current > count)
          for j in [count..(current - 1)]

        this.updateGutterWidth() if current != count

      # Set whether or not the gutter should be visible.
      lineNumbers: (bool) ->
        if bool == true and !this.number
            .prepend('<div class="gutter"></div>')
            .css(left: 20)
        else if bool == false and this.number
            .css(left: 1)
        this.number = bool

      # Return the gutter (a jQuery object).
      gutter: () ->
        this._gutter ?= $(this.element).children("div.gutter")
        return this._gutter

      # Return a jQuery `<ul>`. Each `<li>` is a line of the source viewer.
      lines: ->
        return $(this.element).children('ul')

      # A hash of syntax highlighting rules.
      rules: ->
        return this._rules

    # Re-highlight the text.
    $(".editor > ul").live 'keyup', (event) ->
      # 13:              Enter
      # 37, 38, 39, 40:  Arrow Keys
      # 33, 34:          Page up / down
      # 16, 17, 18, 91:  Shift, Ctrl, Alt, Meta
      # 35, 36:          Home / end
      if !(event.which in [13, 37, 38, 39, 40, 33, 34, 16, 17, 18, 91, 35, 36]) and !event.altKey and !event.ctrlKey
        # Prevent an annoying error when backspacing to the beginning of a line.
        selection = window.getSelection()
        # Store the cursor position before highlighting.
        cursorPos = selection.getRangeAt(0)
        if cursorPos.getClientRects()[0]
          clickx = cursorPos.getClientRects()[0].left
          clicky = cursorPos.getClientRects()[0].top
          # Highlight
          $li = $(selection.focusNode).closest("li")
          rules = $li.closest(".editor").editor('rules')
          highlight.highlight($li, rules)
          # Restore cursor position.
          cursorPos = document.caretRangeFromPoint(clickx, clicky)

    # Line numbering update.
    $(".editor > ul").live 'keydown', (event) ->
      # Redo line numbering for Enter, Backspace, Delete.
      if (event.which in [13, 8, 46])
        $this = $(this)
        newline = switch event.which
          when 13 then 1
          when 8  then -1
          else 0
        $this.parent().editor('updateLineNumbers', newline)
        # Correction
        setTimeout(() ->
          $this.parent().editor('updateLineNumbers', 0)
        , 300)

    # ##################### MAIN ##########################
      .append("<div id='sourceview'></div>")
        position: 'absolute'
        left:   1
        right:  1
        top:    1
        bottom: 1
      .editor('theme', 'plugins/editor/themes/idlefingers.css')
      .editor("highlight", "javascript")
      .editor("lineNumbers", true)

  return editor

3 Answers 3


Yeah, coffeescript doesn't really improve method chaining, of which jQuery is so fond. A couple of tricks. First, remember how powerful destructuring is


    if cursorPos.getClientRects()[0]
      clickx = cursorPos.getClientRects()[0].left
      clicky = cursorPos.getClientRects()[0].top

could be

if r = cursorPos.getClientRects()[0]
    {left, top} = r

also bear in mind


is the same as



 highlight: (language) ->
    this.language = language

could be written

 highlight: (@language) ->

Finally, consider the use of closures for something you keep doing, unless performance is really critical.


$this.parent().editor('updateLineNumbers', newline)
setTimeout(() ->
    $this.parent().editor('updateLineNumbers', 0)
    , 300)

could be

updateLineNumbers = (p) -> $this.parent().editor 'updateLineNumbers', p
updateLineNumbers newLine
after 300, () -> updateLineNumbers 0

One more thing. I almost always rewrite my own version of setTimeout and setInterval when using CoffeeScript, so I can use a cleaner syntax when callbacks are the last argument.

after = (ms, cb) -> setTimeout cb, ms
every = (ms, cb) -> setInterval cb, ms

// that way, instead of this
setTimeout(() ->
), 100)

// you can use this
after 100, () ->


Here are some simple suggestions:

  1. Put some spaces in between lines of code. Some whitespace will make things easier to read
  2. I noticed you are using two spaces for indentation. In general, four spaces (or a tab) makes for more readable code
  3. Don't break lines on chained methods unless you have a ton of them. For example, $(this.element).css(left: 1) can all go on one line no problem. If you have more than 2 or 3, placing each chained method on a new line is a good idea.
  4. Easy on the comments. Commenting your code is good, but too much writing and it inhibits the readability of your code. If you have to write a lot of stuff, put it in your documentation instad. For example, you shouldn't include the key bindings of all those numbers.
  5. Rather than pass a long string as an argument to a function, store it in a local variable on the preceding line, then pass the variable. Instead of:

    $(this).html('bigass html string');

    do this:

    htmlStr = 'bigass html str";


  6. Take advantage of coffeescript's array syntax

    keys = [
        37, 38, 39, 40
        33, 34
        16, 17, 18, 91
        35, 36

  7. Use @property, which coffeescript makes available as shorthand for this.property
  8. Try programming with classes, and keeping as much of your jQuery event bindings in a separate area of your code. That way you can keep all of the $'s and other jQuery junk out of the code that actually makes your app work. Organizing your code into a structured class hierarchy will introduce some much-needed modularity to your coding. Breaking up chunks of commonly used code into reusable modules will make things easier to read and encourage best practices.

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