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'use strict';
const pTry = require('p-try');
const pLimit = concurrency => {
if (!((Number.isInteger(concurrency) || concurrency === Infinity) && concurrency > 0)) {
return Promise.reject(new TypeError('Expected `concurrency` to be a number from 1 and up'));
}
const queue = [];
let activeCount = 0;
const next = () => {
activeCount--;
if (queue.length > 0) {
queue.shift()();
}
};
const run = (fn, resolve, ...args) => {
activeCount++;
const result = pTry(fn, ...args);
resolve(result);
result.then(next, next);
};
const enqueue = (fn, resolve, ...args) => {
if (activeCount < concurrency) {
run(fn, resolve, ...args);
} else {
queue.push(run.bind(null, fn, resolve, ...args));
}
};
const generator = (fn, ...args) => new Promise(resolve => enqueue(fn, resolve, ...args));
Object.defineProperties(generator, {
activeCount: {
get: () => activeCount
},
pendingCount: {
get: () => queue.length
},
clearQueue: {
value: () => {
queue.length = 0;
}
}
});
return generator;
};
module.exports = pLimit;
module.exports.default = pLimit;
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