The following provide answers to common Mojito problems. See also the Mojito: FAQ.


Q: I am trying get config values using ‘ac.config.get(key)’, but Mojito is giving me an error or the value is not found.

A: Try inspecting the spec object that is found in the ActionContext object for the key. If ac is the ActionContext object, you can access the specs object with the following: ac.config.getAppConfig().specs.

If you need to examine the entire ActionContext object, you can use the console.log(ac) or the following code:

Object.keys(ac).forEach(function(n) {
   console.log(n + ' value:');

Q: I am getting the message that my mojit controller is not an object? What does this mean and how do I fix the problem?

A: Usually, this error occurs when one of your controllers has a syntax error. Use the mojito command with the option jslint as seen below to check the app and your mojits for errors:

$ mojito jslint app {app_name}
$ mojito jslint mojit {app_name}/mojits/{mojit_name}

The output from the above commands will tell you if you have errors, but not where the errors are. Use your own developer tools or manually check your controllers for errors and then run your application again.

Q: I am including CSS files in the assets object of ‘application.json’, so why are my CSS files not being inserted into the HTML page?

A: To configure Mojito to automatically insert the asset files specified in the assets object of application.json, you must use the HTMLFrameMojit. The HTMLFrameMojit will insert the assets into the head element if you include the assets in the top array or at the bottom within the body element if you include the assets in the bottom array.

In the example application.json below, the index.css file will be included in the head element of the HTML page. Note that the assets object is inside the frame mojit instance. which is of type HTMLFrameMojit.

    "settings": [ "master" ],
    "specs": {
      "frame": {
        "type": "HTMLFrameMojit",
        "config": {
          "child" : {
            "type" : "framed"
          "assets": {
            "top": {
              "css": [

Q: My binder is getting deployed to the client, so why isn’t the “init” function being called?

A: Most likely Mojito was not able to create a instance to wrap the DOM nodes that wrap mojit instances because the root element of the mojit’s template didn’t have the id value . If your template wraps its content in a <div> element, assign the value to the id attribute of that <div>

element: <div id=>

Q: I am getting Handlebars rendering errors. Is this a client-side or server-side issue with Handlebars and can it be fixed?

A: The issue is not with Handlebars on the client, but with the Handlebars rendering engine on the server. The Handlebars rendering engine inspects the prototypes during the template processing stage. If you remove the prototype inspecting, e.g., creating object literals, the Handlebars engine cannot process the data for the templates.

Although not a permanent solution, you can use Y.mix to ensure that your data has a prototype so that your templates can be rendered. Try doing the following: ac.done(Y.mix({},data));

Q: Why can’t my controller access the YUI modules in the “yui_modules” directory?

A: A common problem is that the YUI module is missing the affinity or that the affinity is incorrect. If your controller has been deployed to the client, your YUI module should have the client or common affinity. If your controller is running on the server, the YUI module should have the affinity server or common. Also, confirm that the registered name of the YUI module, i.e., the string passed to YUI.add, is the same as the string passed to the requires array.

Q: Why am I getting the error message “EADDRINUSE, Address already in use” when I try to start Mojito?

A: You probably have an instance of mojito already started/running (check the output from ps aux | grep mojito). Either stop the instance that is running or start a new instance on another port such as in $ export PORT=8667; node app.js. Your app.js has to have a line of code to set the port or use the environment variable PORT.

Q: When I execute child mojits with “composite.execute”, the views are being rendered, but the binders are not executed. Why?

A: The problem may be that you need to pass the “meta” information to your children as well. This is where the binder metadata bubbles up from the children.

Try doing the following:

  ac.composite.execute(cfg, function(data, meta){
    ac.done(data, meta);
Q: *Why am I getting a DOM dependency error on the server similar to the one below?
How do I debug this type of error?*
TypeError: Cannot read property 'documentElement' of null at Object.YUI.add.requires [as fn]


at proto._attach


A: Your application has modules that depend on DOM APIs that aren’t available in a Node.js-environment. To find those modules, try using the commands mojito gv --trace dom and mojito gv --trace dom-base, which create a graph of the module dependencies.