auto-expanding textarea angular directive. possibly the simplest implementation of this behavior for modern browsers.

kExpandingTextarea

angular.module('kExpandingTextarea', [])
 
.directive('kAutoExpandTextarea', function () {
  return {
    restrict: 'A',
    require: 'ngModel',
    link: function (scope, el, attrs, ctrls) {
      if (!(/textarea/i.test(el[0].tagName))) return;
      
      var handler = function handler (e) {
        el[0].style.height = (attrs.minHeight || '36px');
        el[0].style.height = el[0].scrollHeight + 'px';
      };
      
      // works better with both listeners. means twice the computational overhead...
      var watcher = scope.$watch(function () { return el.val() }, handler);
      el.on('keyup', handler);
      
      scope.$on('$destroy', function () {
        watcher(); // release watcher
        el.off('keyup', handler);
      });
    }
  }
});