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);

    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();
  }
});

@LFDM Thanks, your solution is quite elegant. Although you may want to add focus event, so you can expand textarea by entering it, when you loaded a page and have some text inside it already.

Good solution, I would change event handler a bit to handle paste event with the right mouse button, which is often used to copy paste stuff

element.bind('keyup paste', function(){setTimeout(update, 0);});

my solution, for angular and bootstrap with form-control class, using shadow textarea (without fixing input data)

function autoGrow() {
    return {
        restrict: 'A',
        link: function (scope, element, attr, ctrl) {
            var minHeight = element[0].offsetHeight;

            //create shadow textarea
            var $shadowtx = angular.element('<textarea></textarea>').css({
                position: 'absolute',
                top: -10000,
                left: -10000,
                resize: 'none',

            });
            element.css({resize: "none"}).parent().css({ position: "relative" });
            $shadowtx.addClass("form-control");
            //add to element parent
            angular.element(element.parent()[0]).append($shadowtx);

            var update = function (addtext) {
                addtext = addtext || " aaa"; //when line is ending show new line
                $shadowtx.val(element.val() + addtext);
                element.css('height', Math.max($shadowtx[0].scrollHeight + 5 /* the "threshold" */, minHeight) + 'px');
            }

            //on enter catch keydown, but simulate adding enter
            element.bind('keydown', function (event) {
                var keyc = event.keyCode || event.which;
                if (keyc == 13) {
                    update("\n aaa");
                }
            }).bind('keyup', function (event) {
                var keyc = event.keyCode || event.which;
                document.title = keyc;
                if ((keyc == 46) || (keyc==8)) { //delete, backspace, not fired by scope.$watch
                    update();
                }
            });

            //watch model binding
            scope.$watch(attr['ngModel'], function (v) {
                update();
            });
            //watch show
            scope.$watch(attr['ngShow'], function (v) {
                update();
            });

            update();
        }
    };
};

Thanks . my adjusted version added below makes sure that there are no extra spaces added under the text

• I used $timeout to make sure the shadow element's sizes are set after the current element is rendered and we have the correct size of the text
• For textarea style i have set a height / min-height:

textarea{resize: none; box-sizing: content-box; height: auto; overflow: hidden;}
textarea.form-control{ min-height: 16px; height: 16px;  width: 100%;  }

• Sample usage

<textarea class="form-control word-wrap" auto-size placeholder="Set Location…" ng-model="item.address" ui-focus="isInTabFocus(listIndex, 1)" tabindex="{{getTabIndex(listIndex,1)}}"></textarea>

• sample result
  

  .directive('autoSize', ['$timeout', function($timeout) {
    return function (scope, element, attr, ctrl) {
      var minHeight;
      var $shadowtx = angular.element("<textarea class='" + attr['class'] + "'></textarea>");
      //add to element parent
      angular.element(element.parent()[0]).append($shadowtx);
      element.css({resize: "none"}).parent().css({ position: "relative" });
  
      var update = function (addtext) {
        $shadowtx.val(element.val() + (addtext ? addtext: ''));
        element.css('height', Math.max($shadowtx[0].scrollHeight, minHeight) + 'px');
      };
  
      element.bind('keydown', function (event) {
        var keyc = event.keyCode || event.which;
        if (keyc == 13) {
          update("\n");
        }
      }).bind('keyup', function (event) {
        var keyc = event.keyCode || event.which;
        if ((keyc == 46) || (keyc==8)) { //delete, backspace, not fired by scope.$watch
          update();
        }
      });
  
      $timeout(function(){
        minHeight = element[0].offsetHeight;
        $shadowtx.css({
          position: 'absolute',
          top: -10000,
          left: -10000,
          resize: 'none',
          width: element.width(),
          height: element.height()
        });
        update();
      }, 0);
  
      scope.$watch(attr['ngModel'], function(v){update();});
    }
  }]);
  

@symonny - works great OOTB. Nice!

It doesn't work if ng-model is set by code (controller). Like I fetch text from server and set it there on success so it doesn't set proper height.