Adding JS with library without jquery or jquery-once dependency

If you want to add some JS code, like some kind of snippet to your pages with libraries.yml, add it as any other library item but don't use jquery or drupal behaviours in .js code, add some plain JS code like

document.addEventListener("DOMContentLoaded", function() {

so to wrap some JS snippet for it, do it like below.

Adding prefix or suffix to entity base fields

When creating custom entity you will use "BaseFieldDefinition" code snippets where you will define many things about this field, one of the things you may want to define is suffix or prefix that will be used in display of this field either on entity view or on views that use this field. To do that you will add it to setSettings array simple as 'suffix' => '%'

Useful form snippets for multiple selections

When building forms it is useful to have widgets that select multiple values for you and enhance UI, if you have large select list I would recommend to use select2 module to make custom form use its widget you should first get an array of elements in a variable, like 

Fastly and other CDN batch error

As Batch is dependent on the order of query string parameters if you are using Fastly or some other CDN they often have "Query String Sort" enabled or it is a good practice to do that, as it will result in more cache hits for you.

Make patch from current diff in module

Want to make a quick patch for changes you made in some contrib module to submit it to d.org ?
Write down this and submit the file

git diff  > my_changes.patch

 

To change paths of the patch use 

git diff --src-prefix=a/new/ --dst-prefix=b/new/

like stated here

Get all methods you can run on fields

To get all method names you can run on any field added to any entity, input this into devel/php

ksm(get_class_methods('\Drupal\Core\Field\FieldItemList'));