ix/asynciterable/operators/debounce.mjs

The Interactive Extensions for JavaScript

import { __asyncGenerator, __await, __awaiter } from "tslib";
import { AsyncIterableX } from '../asynciterablex.mjs';
import { AbortError, throwIfAborted } from '../../aborterror.mjs';
/** @ignore */
export class DebounceAsyncIterable extends AsyncIterableX {
    constructor(source, time) {
        super();
        this._source = source;
        this._time = time;
    }
    [Symbol.asyncIterator](signal) {
        return __asyncGenerator(this, arguments, function* _a() {
            throwIfAborted(signal);
            let done = false;
            let reject = () => {
                /**/
            };
            let resolve = () => {
                /**/
            };
            let promise = new Promise((r1, r2) => {
                resolve = r1;
                reject = r2;
            });
            (() => __awaiter(this, void 0, void 0, function* () {
                let id = null;
                const emitValue = (value) => {
                    id = null;
                    resolve(value);
                    promise = new Promise((r1, r2) => {
                        resolve = r1;
                        reject = r2;
                    });
                };
                if (signal) {
                    signal.addEventListener('abort', () => {
                        done = true;
                        if (id) {
                            clearTimeout(id);
                        }
                        id = null;
                        reject(new AbortError());
                    }, { once: true });
                }
                try {
                    let result;
                    // @ts-ignore
                    const it = this._source[Symbol.asyncIterator](signal);
                    // 1. check `!done`
                    // 2. await next value
                    // 3. check `!done` again, in case the signal aborted while the promise was pending
                    while (!done && !(result = yield it.next()).done && !done) {
                        if (id) {
                            clearTimeout(id);
                        }
                        id = setTimeout(emitValue, this._time, result.value);
                    }
                }
                catch (e) {
                    reject(e);
                }
                done = true;
            }))();
            while (!done) {
                yield yield __await(yield __await(promise));
            }
        });
    }
}
/**
 * Emits a notification from the source async-iterable only after a particular time span
 * has passed without another source emission.
 *
 * @template TSource The type of elements in the source sequence.
 * @param {number} time The timeout duration in milliseconds
 * @returns {MonoTypeOperatorAsyncFunction<TSource>} An operator function which debounces by the given timeout.
 */
export function debounce(time) {
    return function debounceOperatorFunction(source) {
        return new DebounceAsyncIterable(source, time);
    };
}

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