To get started, let's get back to how to include custom javascript files to our theme. In the .libraries.yml file, you need to include js:
It is important to follow the indentation so that it is in two spaces. So, we have included the js/custom.js file. But this is not enough for jQuery to work for us. The fact is that the Drupal core does not require jQuery and jQuery does not include. It must be included separately:
JavaScript & jQuery / Prototype Projects for $10 - $30. I am using Drupal-8, Content Type: Basic Page New Field added with following details: Field Name: Methods Field Type: Text (formatted, long) Allowed Number of Values: 10 Field is of Text (formatted.
Project Name: jQuery UI filter Drupal.org project Link: jQuery UI filter Created: 2015-12-18 Last Update: 2016-05-15 Current Version: 8.x-1.0-beta1 Download jQuery UI filter 8.x-1.0-beta1 Version From Drupal.org: Download. 8.9.x core/assets/vendor/jquery.ui/themes/base/sortable.css; 8.0.x core/assets/vendor/jquery.ui/themes/base/sortable.css; 8.2.x core/assets/vendor/jquery.ui/themes. Install the Drupal 8 Modules & Add Image Content. Start: Using either the Upload, FTP, URL, Git.
We will also use jQuery.once(), this is a separate plugin for jQuery, in order to attach events and methods to the selector only once.
The fact is that we will write javascript code that will be called by Drupal several times for different events. Therefore, we will need this .once() method.
Now let's add some code to the custom.js file:
Let's take it in order.
We wrap jQuery code in this construct because jQuery in Drupal runs in .noConflict () mode. This is necessary in order to use the dollar sign $, and this did not conflict with other javascript frameworks Prototype, MooTools. It is unlikely that you will have to meet with these frameworks; jQuery has tightly taken a leading position. But you will have to wrap all jQuery code in this construct.
So we come to the behavior. If you write jQuery code in Drupal, you need to first wrap it in function ($), and secondly in behavior. The behavior name must be unique, in our example myModuleBehavior, but you need to write a name for each behavior:
Use camelCase to name the behavior. Behavior is called when the page loads, for every AJAX request. Thus, when new content is uploaded to the site and embedded in the structure of the existing site, the code from behavior is called, each time. This is significantly different from:
which is called only once upon loading the page.
If you started using behaviors and noticed that you have strange events with the site, for example, through jQuery, a block is added several times:
For each ajax request, you will add another Test paragraph. Therefore, you need to add the .once() function:
Another feature of behavior is the context variable. Each time new content is added to the site when the page is loaded or through ajax, then all new content is in the context variable. Thus, we do not need to go through the entire DOM tree, after each ajax request, to attach the event to the selector. Just context is enough:
Now the paragraph is written in the correct Drupal style. Of course, you can use the old entry with document.ready (), but then it will only work once and slower than through behavior.
If you have any questions about jQuery/javascript or suggestions for additional theme, write in the comments.
View the discussion thread.
I was editing a custom block in a Drupal 8 site that I'm working on and needed to use jQuery for a quick image swap. While it would have been possible to accomplish what I was looking for in straight JavaScript, doing it in jQuery made things much easier. The only problem was that jQuery wasn't working and I was getting the 'Uncaught ReferenceError: $ is not defined' message. I knew that jQuery was already being called by my theme, so why wasn't it working?
After a bit of digging, I discovered two things that were keeping jQuery from working in my Drupal block:
- Drupal uses jQuery.noConflict() mode, so the $ shorthand won't work out of the box. This means, to select the div1 div, for example, you'd need to use
jQuery.('#div1')instead of$('#div1'). Or, apparently, you can 'include jQuery and Drupal as dependencies in the library definition in your MODULE.libraries.yml and add a wrapper around your function,' but that sounds like a lot of work. I chose to go the easy route for this one because it was such a small bit of code. - To improve performance, Drupal calls jQuery from the very bottom of the page so, if you're including JavaScript in a custom block, it's going to fire before jQuery is available. (Yes, I know that it would theoretically be better to put all the JavaScript into an external file, but when it's just a couple lines of code, that feels like more effort than it's worth.) The good news is that there's an easy fix: You can keep your script from firing until jQuery has loaded with window.onload.
Put together, here's what those workarounds look like:
Problem solved! The above works from within a Drupal 8 custom block.
This also works as a cheap way to get jQuery code to run from within the body of any Drupal 8 content node. Here's a quick test I used to make sure it was working:
Drupal 8 Jquery Plugin
Without the window.onload you get 'Uncaught ReferenceError: jQuery is not defined,' but with it there, your title fades out as soon as the page finishes loading.
Drupal 8 Jquery Once
This article was written by Robert James Reese on September 21st, 2017 and was last updated on February 27th, 2021. Before using any of the code or other content in this post, you must read and agree to our terms of use.
