default-passive-events   

> Makes {passive: true} by default when EventListenerOptions are supported

50 lines snippet that enables passive event listeners by default for some events (see list below). It basically will set { passive: true } automatically every time you declare a new event listener.

Installation

``bash
yarn add default-passive-events
`

Usage

Simply import the package:

`javascript
import 'default-passive-events';
`

or require it:

`javascript
require('default-passive-events');
`

or include it locally:

`html
type="text/javascript"
src="node_modules/default-passive-events/dist/index.js"
>
`

or from unpkg CDN:

`html
type="text/javascript"
src="https://unpkg.com/default-passive-events"
>
`

Bundle formats

This package is distributed as multiple, different types of output bundles. The most often your bundler will properly choose the correct version by itself.

To get more information about supported bundle formats have a look at official microbundle documentation. Especially interesting is the modern format which - if used properly with your bundle system - might produce significantly smaller output code.

Examples

Those are some examples and their output:

`javascript
document.addEventListener('mouseup', onMouseUp); // {passive: true, capture: false}
document.addEventListener('mouseup', onMouseUp, true); // {passive: true, capture: true}
document.addEventListener('mouseup', onMouseUp, false); // {passive: true, capture: false}
document.addEventListener('mouseup', onMouseUp, { passive: false }); // {passive: false, capture: false}
document.addEventListener('mouseup', onMouseUp, {
passive: false,
capture: false,
}); // {passive: false, capture: false}
document.addEventListener('mouseup', onMouseUp, {
passive: false,
capture: true,
}); // {passive: false, capture: true}
document.addEventListener('mouseup', onMouseUp, {
passive: true,
capture: false,
}); // {passive: true, capture: false}
document.addEventListener('mouseup', onMouseUp, {
passive: true,
capture: true,
}); // {passive: true, capture: true}
`

Demo

Check the demo page for a working example.

Motivation

Just to take benefit in your apps without having to edit every single event listener you already have.

Targeted events

Default-passive-events package makes following event listeners passive by default:

- scroll
- wheel
- touchstart
- touchmove
- touchenter
- touchend
- touchleave
- mouseout
- mouseleave
- mouseup
- mousedown
- mousemove
- mouseenter
- mousewheel
- mouseover
- animationstart
- animationend
- animationiteratio
- transitionstart
- transitionend
- transitionrun
- transitioncancel

Configuration

You can configure library to override different set of events than the default ones.
To do that set the window.defaultPassiveEvents_supportedPassiveEvents property like so:

`javascript
window.defaultPassiveEvents_supportedPassiveEvents = ['scroll', 'wheel'];
`

Q&A

$3

Well, that's true, partly. First of all specification says that you shouldn't ever try to preventDefault from the context of passive listener. But if that's not a possibility you should know that in the console you see only _error-looking log messages_, which are _not actual errors_ (ergo: they _do not break your code_).

$3

Unfortunately, no. Since they are not actual errors there is no way to catch them and (more importantly) there is no way to distinguish whether you're inside of the passive listener context to know when not to call/override preventDefault method. Now, we look at the regarding issue in WHATWG repo whatwg/dom#587.

$3

Yes, original addEventListener is available under _original property of our's addEventListener's implementation (so - element.addEventListener._original). Having that in mind, you can bring it back for however you want, e.g.:

`javascript
element.addEventListener = element.addEventListener._original;
`

Resources

- About passive event listeners https://medium.com/@devlucky/about-passive-event-listeners-224ff620e68c
- EventListenerOptions https://github.com/WICG/EventListenerOptions
- Explanation https://github.com/WICG/EventListenerOptions/blob/gh-pages/explainer.md
- Polyfill https://github.com/WICG/EventListenerOptions/blob/gh-pages/EventListenerOptions.polyfill.js
- Spec https://dom.spec.whatwg.org/#dictdef-eventlisteneroptions
- Chrome feature https://www.chromestatus.com/features#passive
- About scrolling performance https://plus.google.com/+RickByers/posts/cmzrtyBYPQc
- Nice Chrome blog article https://blog.chromium.org/2016/05/new-apis-to-help-developers-improve.html

Publishing

To release, simply run npm version and then pnpm publish`.

Author

@zzarcon

Maintainers

@zzarcon
@frsgit