优化

‘liusuyi’

2023-10-21 ae92b6823499cfab77201b4033922fa373fb37a3

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'use strict';
const AggregateError = require('aggregate-error');
 
module.exports = async (
    iterable,
    mapper,
    {
        concurrency = Infinity,
        stopOnError = true
    } = {}
) => {
    return new Promise((resolve, reject) => {
        if (typeof mapper !== 'function') {
            throw new TypeError('Mapper function is required');
        }
 
        if (!(typeof concurrency === 'number' && concurrency >= 1)) {
            throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${concurrency}\` (${typeof concurrency})`);
        }
 
        const ret = [];
        const errors = [];
        const iterator = iterable[Symbol.iterator]();
        let isRejected = false;
        let isIterableDone = false;
        let resolvingCount = 0;
        let currentIndex = 0;
 
        const next = () => {
            if (isRejected) {
                return;
            }
 
            const nextItem = iterator.next();
            const i = currentIndex;
            currentIndex++;
 
            if (nextItem.done) {
                isIterableDone = true;
 
                if (resolvingCount === 0) {
                    if (!stopOnError && errors.length !== 0) {
                        reject(new AggregateError(errors));
                    } else {
                        resolve(ret);
                    }
                }
 
                return;
            }
 
            resolvingCount++;
 
            (async () => {
                try {
                    const element = await nextItem.value;
                    ret[i] = await mapper(element, i);
                    resolvingCount--;
                    next();
                } catch (error) {
                    if (stopOnError) {
                        isRejected = true;
                        reject(error);
                    } else {
                        errors.push(error);
                        resolvingCount--;
                        next();
                    }
                }
            })();
        };
 
        for (let i = 0; i < concurrency; i++) {
            next();
 
            if (isIterableDone) {
                break;
            }
        }
    });
};