Adding a JavaScript event handler to a form


Need to make your PFG forms more dynamic? It’s easy to add JavaScript.

There are two basic steps to injecting JavaScript into a PFG form:

  1. Use the Management Interface to create a text file (object type: file; mimetype: text/plain) either inside the form folder or in a skin folder;

  2. Use the form folder’s edit / overrides pane, header injection field to tell PFG to inject it into the form.


Let’s look at the second step first. Let’s say that your JavaScript file is named form_js. Then just specify:


in the header injections override field.


There are a couple of considerations here:

  1. Since this is a header injection, you’ll need to supply the SCRIPT tags;

  2. You’ll nearly certainly want to use jQuery to attach the event handler, since jQuery is part of Plone.

jQuery(function($) {
    $('#my-questions :input')
        .click(function() {
            alert('checkbox clicked');

This code fragment shows off both, and attaches an alert to every input in the mqy-questions field.

Note the use of the common jQuery idiom:

jQuery(function($) {

This accomplishes a couple of things:

  1. it sets the code up to run once the page is loaded;

  2. it aliases “jQuery” to “$” so that we may use common jQuery shorthand.

An alternative injection

If you want to use a separate JavaScript file that is actual JS (no script tags) and will be shared among forms, use the header injection override like this:

string:<script src="form_scripts.js" />

assuming your script is named form_scripts.js. You may make it a little more sophisticated if you need an absolute URL:

string:<script src="${here/form_scripts.js/absolute_url}" />

using TALES string interpolation.