# Extend components and plugins with EXTENSION
> Add behavior to an existing component from outside, without editing its source, with EXTENSION().
Framework: jcomponent20
Product: jComponent 20 (jcomponent@20)
Language: en
Content-SHA256: 36d8b89a461439666c01affaa521ef83de6b58de563a0bdc49c5d9cc976298f2
Snapshot: c0700e321579725c5cf4f5ace1ad7d2866d1b4f93c24a63c0b41b6b7998e976c
Sources: jcomponent20@3fedd009a277f50fddc608b97afbec553b67c51b
Review: not-recorded
`EXTENSION(name, config, callback)` adds code to every instance of the component `name` (or of the plugin `@name`) when it is created. The callback receives the instance and its config, exactly like a declaration, so you can add methods, change options or listen to events. It is how an application customizes third-party components without forking them.
```html public/index.html
jComponent
```