I am currently registering custom blocks via javascript only. I am building a site with lots of custom layouts and widgets, and I'm using the new custom blocks of Gutenberg to facilitate content creation using these custom layouts.

I have a few Custom Blocks, but I did not want to create a Plugin for each block, so I decided to group all the blocks together inside my theme. I created directory for each block, and each directory has an block.js file, which registers the block via the javascript function wp.blocks.registerBlockType.

Sample block.js

const { registerBlockType } = wp.blocks;
registerBlockType( 'myguten/test-block', {
    title: 'Basic Example',
    icon: 'smiley',
    category: 'layout',
    edit() {
        return <div>Hola, mundo!</div>;
    save() {
        return <div>Hola, mundo!</div>;
} );

Here is the sample folder structure for my blocks:


I have webpack configured to bundle all my block.js files into one file called dist/blocks.build.js. And in my functions.php, I load my blocks.build like so:

function enqueue_custom_blocks() {
    wp_enqueue_script('custom_blocks', get_stylesheet_directory_uri() . '/dist/blocks.js', array('wp-blocks'));


add_action( 'enqueue_block_editor_assets', 'enqueue_custom_blocks');

This setup totally works. I am able to work on my custom blocks right in my theme folder, and I have no problem using these custom blocks on my pages and posts.

Therefore, I am curious, what is the purpose of the php function register_block_type? Furthermore, is there anyway I could use register_block_type to register blocks in bulk? My only real reason for wanting to use register_block_type is to leverage the render_callback option if, for example, [my block needed to be dynamic and leverage server-side rendering. Can I apply a filter to a block?

1 Answer 1


1.: The register_block_type lets you load additional stylesheets and scripts for your block in the frontend

2.: As you yourself wrote, register_block_type lets you define a dynamic php render_callback function

3.: If you use a render_callback, you can of course use filters within it.

EDIT: As the comments pointed out, there is some clarification needed on how to use custom filters

Firstly, you can make the whole function pluggable just by wrapping it into a function_exists like this

'render_callback' => 'my_awesome_block_render'));

  function my_awesome_block_render($attributes,$context){

Secondly: Filters.

Wordpress filters are an interesting thing. The long and short is the following: Whenever you call $var =apply_filters('my_cool_filter_name',$var);, Wordpress looks into its global filter function array if a function is registered for the filter "my_cool_filter_name". So for using a custom filter, you just think of a name that hopefully isn't taken by any other plugin/function and apply_filters to it.

So, to use filters to change some aspects of your blocks render, you just use apply_filters with whatever you wish. Let's have an example with a slider block:

function my_awesome_slider_block_render_function($attributes){ //do whatever stuff you want $slider_speed = apply_filters('my_awesome_slider_block_slider_speed',$attributes['slider_speed']); //whatever else }

if nobody added a filter to "my_awesome_slider_block_slider_speed", the variable $slider_speed contains now $attributes['slider_speed'].

However, if for some reason you need to change this speed, (let's say, you use a child theme for mobile devices and the slider should be slower on mobile devices), you can just add a filter in your functions.php like this:

function change_the_mobile_speed($slider_speed){
  return 800;

The same works for actions, too.

Happy Coding!

  • What are exactly those filters? I found this demo which is helping me understand the inner workings of custom blocks. He is using a filter, ie: add_filter( 'gutenberg_post_list_render_filter', 'render_guten_post_list_filter', 10, 2 ); I don't understand how he came up with the name of that hook. Nonetheless, this explanation is helpful in understanding the role of register_block_types Feb 26, 2019 at 19:51
  • @JeffWilkerson that is a custom filter he is using for that plugin, you can see it applied using apply_filters( 'gutenberg_post_list_render_filter'... in the render.php file. I'm also interested in knowing what is @kuchenundkakao meaning in point 3.
    – Alvaro
    Feb 26, 2019 at 22:57
  • @Alvaro Yes I know that is a custom function, I am curious how he registers the filter. Obviously, Wordpress is sniffing for filters named {my_cool_block}_render_filter, and calling it if the function exists. I've seen this type of thing before, where you can hook into some functionality by just suffixing your function with a common identifier. I just don't know how he came up with that exact name. I don't see the key 'gutenberg-post-list' being defined anywhere. Feb 28, 2019 at 2:09
  • On second thought, I see comments in the repo that the demo no longer works. So it seems that there is not a filter that I can tap into on the fly, and the only way I can control whats rendered is to leverage the render_callback option when registering the block Feb 28, 2019 at 2:14
  • I edited the answer and i hope this clarifies the usage of filters ;) Feb 28, 2019 at 7:41

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