Cancellation Token

Tokens are extremely lightweight and easy to grok, their power lies in
their composability. The entire implementation is this:

``js
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;
}
}
`

Usage

Each example builds on the previous in order.

create
`js
import Token from 'cancellation-token';

let token = new Token();
`

conditional work
`js
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
`js
let scheduledJob = schedule(() => { alert("hello world!"); });
scheduledJob.cancel();
`

inheritance
`js
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();
``