Created
March 30, 2024 13:54
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Async event polling in JavaScript. Just a proof-of-concept, not recommended for serious development, even though it's pretty convenient.
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| class Queue { | |
| #start = 0 | |
| #end = 0 | |
| #len = 0 | |
| #cap = 1 << 10 | |
| #cap_mask = this.#cap - 1 | |
| #data = new Array(this.#cap) | |
| enqueue(item) { | |
| if (this.#len == this.#cap) { | |
| this.#data = this.#data.concat(this.#data) | |
| this.#end += this.#cap | |
| this.#cap <<= 1 | |
| this.#cap_mask = (this.#cap_mask << 1) | 1 | |
| } | |
| this.#start = (this.#start - 1) & this.#cap_mask | |
| this.#len++ | |
| this.#data[this.#start] = item | |
| } | |
| dequeue() { | |
| if (this.#len == 0) return null | |
| this.#end = (this.#end - 1) & this.#cap_mask | |
| this.#len-- | |
| return this.#data[this.#end] | |
| } | |
| } | |
| function createPoller(elem, type) { | |
| const events = new Queue() | |
| const resolvers = new Queue() | |
| elem.addEventListener(type, e => { | |
| const r = resolvers.dequeue() | |
| if (r) return r(e) | |
| events.enqueue(e) | |
| }) | |
| return () => { | |
| const e = events.dequeue() | |
| if (e) return Promise.resolve(e) | |
| return new Promise(res => resolvers.enqueue(res)) | |
| } | |
| } |
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