jquery.autoresize.js

/*
 * jQuery autoresize 0.1
 * http://jusbrasil.com
 * Copyright 2013
 * Free to use under the MIT license.
 * http://www.opensource.org/licenses/mit-license.php
 * @author: webteam@jusbrasil.com.br
*/


;(function ( $, window, document, undefined ) {
  "use strict";

  var pluginName = "autoresize",
      defaults = {};

  function Plugin( element, options ) {
    this.element = element;
    this.$element = $(element);

    this.options = $.extend( {}, defaults, options );

    this._defaults = defaults;
    this._name = pluginName;

    this.init();
  }

  Plugin.prototype = {
    getClone: function() {
      // The clone is necessary because when the height of the visible textarea is
      // set as `auto`, the page height and the scrollTop changes. So, when the new
      // height is set, depending of where is the cursor on screen, it disappears.
      // So, the clone is used just to set the new height of the visible textarea.
      // Properties which may effect space taken up by chracters:

      var props = ['height','width','lineHeight','textDecoration','letterSpacing'],
          propOb = {},
          _this = this;

      // Create object of styles to apply in the new HTML element
      $.each(props, function(i, prop){
          propOb[prop] = _this.$element.css(prop);
      });
      propOb = $.extend(propOb, {
        position: 'absolute',
        top: 0,
        left: -9999
      });

      // Clone the actual textarea removing unique properties
      // and insert before original textarea with the properties copied from
      // original element
      return this.$element.clone()
        .removeAttr('id')
        .removeAttr('name')
        .css(propOb)
        .attr('tabIndex','-1')
        .insertBefore(this.$element);
    },

    init: function() {
      var $clone = this.getClone(),
          _this = this;

      function resize () {
        $clone.css('height', 'auto').val(_this.element.value);
        _this.$element.css('height', $clone.get(0).scrollHeight+'px');
      }
      /* 0-timeout to get the already changed text */
      function delayedResize () {
        window.setTimeout(resize, 0);
      }

      this.$element
        .on('change',  resize)
        .on('cut paste drop keydown', delayedResize);

      resize();
    }

  };

  $.fn[pluginName] = function ( options ) {
    return this.each(function () {
      if (!$.data(this, "plugin_" + pluginName)) {
          $.data(this, "plugin_" + pluginName, new Plugin( this, options ));
      }
    });
  };

})( jQuery, window, document );