ix/asynciterable/operators/takewhile.mjs

The Interactive Extensions for JavaScript

import { __asyncGenerator, __asyncValues, __await } from "tslib";
import { AsyncIterableX } from '../asynciterablex.mjs';
import { wrapWithAbort } from './withabort.mjs';
import { throwIfAborted } from '../../aborterror.mjs';
/** @ignore */
export class TakeWhileAsyncIterable extends AsyncIterableX {
    constructor(source, predicate) {
        super();
        this._source = source;
        this._predicate = predicate;
    }
    [Symbol.asyncIterator](signal) {
        return __asyncGenerator(this, arguments, function* _a() {
            var _b, e_1, _c, _d;
            throwIfAborted(signal);
            let i = 0;
            try {
                for (var _e = true, _f = __asyncValues(wrapWithAbort(this._source, signal)), _g; _g = yield __await(_f.next()), _b = _g.done, !_b; _e = true) {
                    _d = _g.value;
                    _e = false;
                    const item = _d;
                    if (!(yield __await(this._predicate(item, i++, signal)))) {
                        break;
                    }
                    yield yield __await(item);
                }
            }
            catch (e_1_1) { e_1 = { error: e_1_1 }; }
            finally {
                try {
                    if (!_e && !_b && (_c = _f.return)) yield __await(_c.call(_f));
                }
                finally { if (e_1) throw e_1.error; }
            }
        });
    }
}
/**
 * Returns elements from an async-iterable sequence as long as a specified condition is true.
 *
 * @template T The type of the elements in the source sequence.
 * @param {((value: T, index: number, signal?: AbortSignal) => boolean | Promise<boolean>)} predicate A function to test each element for a condition.
 * @returns {OperatorAsyncFunction<T, T>} An async-iterable sequence that contains the elements from the input sequence that occur
 * before the element at which the test no longer passes.
 */
export function takeWhile(predicate) {
    return function takeWhileOperatorFunction(source) {
        return new TakeWhileAsyncIterable(source, predicate);
    };
}

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