Auto-Resizing Text Area

jquery.autoResize.coffee

# Auto-Resizing Text Area

# Works in Chrome, Firefox, and IE7+

# notes:
#   * 'rows' and 'cols' attributes should be set on the textarea
#   * 'rows' becomes the minimum number of rows
#   * 'overflow' should be set to 'hidden' and 'height' should be set to 'auto'

# sass:
#   textarea
#     overflow: hidden
#     height: auto
#
# haml:
#   %textarea{ :rows => 5, :cols => 40 }
#
# coffee:
#   $('textarea').autoResize()

$.fn.autoResize = ->
  @each ->
    cols = @cols
    rows = @rows

    grow = ->
      linesCount = 0
      lines = @value.split '\n'
      i = lines.length - 1

      while i >= 0
        linesCount += Math.floor ( lines[i].length / cols ) + 1
        --i

      if linesCount >= rows then @rows = linesCount + 1 else @rows = rows

    $(this).bind keydown: grow, keyup: grow