Integrate External Eidtors with Angularjs

JS editors like TinyMCE, CodeMirror, SimpleMDE are editors for html, code, markdown text respectively, they works fine one their own, but when used with angularjs, some glue code is needed to hook them together. Here is a summary of what is needed:

Take SimpleMDE as example, we walk through those steps one by one:

1. Module & Directive

//create directive "ui-simplemde"
angular.module('uiSimplemde', [])
.directive('uiSimplemde', function($window, $timeout){

the code is simple and self-explanatory, we create its own module uiSimplemde, and define the new directive on the module, now you use this as an external dependency for your angularjs app, and you must include this module in your app module dependency list: angular.module('myApp', ['uiSimplemde']);. Now just add the directive as attribute to the target html element:

<!--create tinymce instance, bind it to the textarea, configuration is supposed to be an configuration object defined on current $scope-->
<textrea ui-simplemde="configuration"></textarea>
<!-- or sometimes, with an inline configuration object-->
<textrea ui-simplemde="{autofocus: true}"></textarea>

2. Editor Construction

This step is simple enough, just create an editor instance and bind it to target DOM element(where the ui-simplemde directive is set), here we do this binding by passing the element to the SimpleMDE() constructor function as configuration value, other editors may has their own way to do this, like an explicit bindTo(ele) or attachTo(ele) api.

function createEditorInstance(options, element){
  //create and bind editor instance by pass element to constructor
  options['element']= element;
  var editor = new SimpleMDE(options);
  //load default value inside target textarea element
  var default_value = angular.element(element).val();
  return editor;

3. Value Synchronization

We need to do bi-directional data binding, when editor value is changed or set/reset, say, by invoking editor commands or shortcuts etc, we want the ngModel to be updated accordingly, and vice versa, when ngModel is set by our app code, the editor instance should update or refresh itself. ngModel is extremely flexible and powerful, it also has two customizable $formatters $parsers $validators and $asyncValidators arrays, you can push your own formatters or parsers or validators into them, those formatters or parsers or validators will be called when value is synced between ngModel.$viewValue to ngModel.$modelValue, read the docs if you want to know more about this.

function syncWithNgModel(editor, ngModel, scope){
  ngModel.$render = function(){
  editor.codemirror.on('changes', function(){
    var newValue = editor.value();
    if(newValue !== ngModel.$viewValue){

4. Watch for Configuration changes

Sometimes, when we may change editor settings on-the-fly, in which case, we may want to watch the configuration object, and get notified when it's changed, and apply the changes accordingly, this can be done by add a listener with $

function watchConfigurations(scope, attrs, editor){
  scope.$watch(attrs.uiSimplemde, function(newVal, oldVal){
    if(newVal !== oldVal){
      //update SimpleMDE configurations

5. Cleanup

Most of the angularjs stuff is hooked on the $scope object, so no manual cleanup is necessary. But the external editors usually has its own resources that need to be cleaned up(especially those event listener registered globally), fail to do so will keep those resources hanging around and thus cause memory leaks. In our editor's case, the leak is not so obvious unless you create tens of editors on the page. But we should always remember to check this and do it if necessary.

//cleanup when $scope is destroyed
scope.$on('$destroy', function(){
  //destroy editor instance, restore to original textarea

The End

With all these tasks done, we call now hook them together, create our ui-simplemde directive.

angular.module('ui.simplemde', [])
.value('simpleMdeConfig', {
.directive('uiSimplemde', uiSimplemdeDirective);

function uiSimplemdeDirective($timeout, $window, simpleMdeConfig){
  return {
    require: '?ngModel',
    restrict: 'A',
    priority: 599,
    link: function(scope, element, attrs, ngModel){
        throw new Error("SimpleMDE is not defined! Is simplemde.js included?");
      //create editor instance
      var default_options = simpleMdeConfig || {};
      var current_options = scope.$eval(attrs.uiSimplemde);
      var options = angular.extend({}, default_options, current_options);
      var editor = createEditorInstance(options, element[0]);
      scope.$mde = editor;
      //setup value synchronization
      syncWithNgModel(editor, ngModel, scope);
      //watch configuration changes
      watchConfigurations(scope, attrs, editor);
      scope.$on('$destroy', function(){
        //destroy editor instance

Besides what we mentioned above, there is one more thing, the configuration, in our directive, we allow you to pass configuration with something like <textarea ui-simplemde="configObj"></textarea> or <textarea ui-simplemde="{name: '', style: ''}"></textarea>, this enables you to configure each editor instance with different options, we also register an global simpleMdeConfig value object, it's has the lower priority, if you want to provide a application-wide configuration for all editor instances, you may override this value or decorate it:

//override the value, by providing new global configuration
angular.module('jsb-admin').value('simplemdeconfig', {
  autodownloadfontawesome: false
  //more options...

//or extend the existing global cnfiguration by decorating it
angular.module('jsb-admin').decorator('simplemdeconfig', function($delegate){
  var newcfg = angular.extend({}, $delegate, {
    autodownloadfontawesome: false,
    //more options...
  return newcfg;

Decorator for values is not documented in angularjs official document(which only show examples for services directive and filters), but it also works.

What next?

This is just a simple walk through of the angularjs editor integration process, we cover the essentials steps here, but there are many other missing features like debounce, validation check, support for disabled attributes etc. There are many examples of angularjs integrations with external editors out there, especially those from, ng-tinymce, ng-codemirror, ng-ace etc, they are good references and examples.