Auto Expanding/Grow textarea directive for AngularJS

gistfile1.js

/**
 * The MIT License (MIT)
 *
 * Copyright (c) 2013 Thom Seddon
 * Copyright (c) 2010 Google
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.

 * Adapted from: http://code.google.com/p/gaequery/source/browse/trunk/src/static/scripts/jquery.autogrow-textarea.js
 *
 * Works nicely with the following styles:
 * textarea {
 *  resize: none;
 *  word-wrap: break-word;
 *  transition: 0.05s;
 *  -moz-transition: 0.05s;
 *  -webkit-transition: 0.05s;
 *  -o-transition: 0.05s;
 * }
 *
 * Usage: <textarea auto-grow></textarea>
 */

app.directive('autoGrow', function() {
  return function(scope, element, attr){
    var minHeight = element[0].offsetHeight,
      paddingLeft = element.css('paddingLeft'),
      paddingRight = element.css('paddingRight');

    var $shadow = angular.element('<div></div>').css({
      position: 'absolute',
      top: -10000,
      left: -10000,
      width: element[0].offsetWidth - parseInt(paddingLeft || 0) - parseInt(paddingRight || 0),
      fontSize: element.css('fontSize'),
      fontFamily: element.css('fontFamily'),
      lineHeight: element.css('lineHeight'),
      resize:     'none'
    });
    angular.element(document.body).append($shadow);
    
    if (attr.ngModel) {
      scope.$watch(attr.ngModel, function() {
        update();
      });
    }

    var update = function() {
      var times = function(string, number) {
        for (var i = 0, r = ''; i < number; i++) {
          r += string;
        }
        return r;
      }

      var val = element.val().replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
        .replace(/&/g, '&amp;')
        .replace(/\n$/, '<br/>&nbsp;')
        .replace(/\n/g, '<br/>')
        .replace(/\s{2,}/g, function(space) { return times('&nbsp;', space.length - 1) + ' ' });
      $shadow.html(val);

      element.css('height', Math.max($shadow[0].offsetHeight + 10 /* the "threshold" */, minHeight) + 'px');
    }

    element.bind('keyup keydown keypress change', update);
    update();
  }
});