Ember addon providing requestAnimationFrame utilities to properly batch reads/writes within Embers runloop.
npm install ember-batcher!CI Build
An Ember addon to batch DOM reads and mutations using requestAnimationFrame.
As noted in Paul Irish's "What Forces Layout", a number of properties or methods, when requested/called, will trigger the browser to sychronously calculate the style and layout. This is also called reflow or layout thrashing, and is common performance bottleneck. This addon attempts to provide a mechanism to compliment Ember's runloop batching to help minimize layout thrashing.
* Ember.js v3.24 or above
* Ember CLI v3.24 or above
* Node.js v14 or above
``bash`
ember install ember-batcher
Register a task function that will get batched with other "reads" and called on the next requestAnimationFrame (if supported). The method will be executed within either the current run loop or will create a new run loop if necessary.
`js
import Component from '@glimmer/component';
import { readDOM } from 'ember-batcher';
export default class MyComponent extends Component {
foo() {
readDOM(() => {
// Perform DOM read
});
}
}
`
Register a task function that will get batched with other "mutations" and before other "reads". The method will be called on the next requestAnimationFrame (if supported). The method will be executed within either the current run loop or will create a new run loop if necessary.
`js
import Component from '@glimmer/component';
import { mutateDOM } from 'ember-batcher';
export default class MyComponent extends Component {
foo() {
mutateDOM(() => {
// Perform DOM mutation
});
},
}
`
Since the purpose of this addon is to minimize layout thrashing, we want to perform _all_ _reads_ before we perform _writes_. Additionally, you should close over values created during the _read_ phase that are used in the _write_ phase. This helps ensure that work doesn't leak outside of the frame we're performing the work in, and allows you to prepare values in the _read_ phase that are used in the subsequent _write_ phase.
To be clear, _writes_ should not occur during the _reads_ phase, therefore you should not have any code that performs any reads from within the callback of readDOM. All _writes_ should occur inside a call to mutateDOM, whether that's in a non-nested call to _mutateDOM itself, or from a nested call to mutateDOM inside of a readDOM call.
Example of _read_ first, then _write_.
`js
import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { readDOM, mutateDOM } from 'ember-batcher';
export default class MyComponent extends Component {
@tracked
width;
foo() {
readDOM(() => {
const width = document.querySelector('.foo').clientWidth;
mutateDOM(() => {
// we should perform our update conditionally, only if the value of width changes. This helps
// minimize unnecessary layout thrashing.
if (this.width !== width) {
this.width = width * 2;
}
});
});
},
}
``
See the Contributing guide for details.
This project is licensed under the MIT License.