elastic.js

angular.module('myApp')
.directive('elastic', [
  '$timeout',
  function ($timeout) {
    'use strict';

    return {
      restrict: 'A',
      link: function ($scope, element) {
        var resize = function () {
          element[0].style.height = 'auto';
          element[0].style.height = '' + element[0].scrollHeight + 'px';
        };
        element.on('blur keyup change', resize);
        $timeout(resize, 0);
      }
    };
  }
]);