ES2015 JS Cancellation Tokens for composable async cleanup
yarn add cancellation-token
Tokens are extremely lightweight and easy to grok, their power lies in their composability. The entire implementation is this:
export default class Token {
constructor(parent) {
this._parent = parent;
this._cancelled = false;
}
get cancelled() {
return this._cancelled || (this._cancelled = this._parent ? this._parent.cancelled : false);
}
cancel() {
this._cancelled = true;
}
}Each example builds on the previous in order.
create
import Token from 'cancellation-token';
let token = new Token();conditional work
let jobs = [];
function cancellableJob(job, token) {
return function() {
if (!token.cancelled) {
job();
}
};
}
function schedule(job) {
let token = new Token();
jobs.push(cancellableJob(job, token);
return token;
}cancelling work
let scheduledJob = schedule(() => { alert("hello world!"); });
scheduledJob.cancel();inheritance
let grandParentToken = new Token();
let parentToken = new Token(grandParentToken);
function scheduleWithParent(job, parentToken) {
let token = new Token(parentToken);
jobs.push(cancellableJob(job, token);
return token;
}
// cancel the task and all descendants
grandParentToken.cancel();
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