AutoScout24 Custom Events

TypeScript definitions for all custom events available on as24 pages

• Installation
• Usage
  • Listen to custom events
  • Firing custom events
• Debugging
• Polyfill
• Contributing
  • Adding custom events
  • Versioning
  • Rollup config

This library provides a glue at compile-time between DOM CustomEvents produced in some component on a page and listeners from other components on that same page that depend on an agreed event interface (name & payload)

Installation

Install as a regular npm package

yarn add @autoscout24/custom-events@latest
or
npm install --save @autoscout24/custom-events@latest

it's important to use the @latest tag so package is always up to date. It wouldn't help to pin to a particular version since at runtime the events will behave like @latest.

Usage

Listen to custom events

To add an event listener somewhere on your page, you do the usual event listener registration on Document root element

// somewhere in your app...
import { ListPage } from '@autoscout24/custom-events'

document.addEventListener(ListPage.ClassifiedListFilterUpdate, e => console.log(e.detail.searchUrls.standard))

the compiler will know that the event is of type e: ListPage.ClassifiedListFilterUpdate since it can use indexed types.

Firing custom events

All custom events should be fired on the top Document root. To fire an event in a typesafe way, you can use the helper strictCustomEvent. It has the same signature as the usual CustomEvent constructor but it's typesafe (will check for consistency between name and payload)

import { ListPage, strictCustomEvent } from '@autoscout24/custom-events'

document.dispatchEvent(strictCustomEvent(ListPage.ClassifiedListTotalCountUpdate, { detail: {
  totalCount: 42
}})

The compiler will make sure that the payload in detail matches the event definition associated to the key.

Debugging

You can log all custom event traffic easily on the browser by pasting the contents of logCustomEvents into the console. This will log all events

Polyfill

A custom polyfill for CustomEvent constructor syntax support on older browsers (IE11 and below) is provided in case you want to add it to your build

Contributing

Adding custom events

To add a new page event:

1. Either go to the existing page where your event is present or create a new page (if it's a global event that ocurrs on all pages add it to "global page").
2. Define both a constant with the event name and type alias with the payload (we exploit Typescript duality to handle types and values under same name)
3. Register the event on the DocumentEventMap so compiler knows about it everywhere. Note that this makes the events available only on the Document DOM element, which is good because that's where we should dispatch them.

Naming convention: To avoid collisions and ensure consistency, CustomEvent names should be of the form <SERVICE>:<NAME>, for example, CLASSIFIED_LIST:FILTER_UPDATE, etc.

Versioning

Since the global events are not really controlled by this library (they are fired by other applications), even if we tag a change as breaking it's not like the consumers will be safe by staying on older versions since at runtime the events will be upgraded. We still use versioning to keep the clients informed of potential breaking changes (ideally there should be none)

Rollup config

Rollup is used to bundle the library. Bundle Statistics are available after build to inspect package size.