72 lines
1.5 KiB
JavaScript
Executable file
72 lines
1.5 KiB
JavaScript
Executable file
'use strict';
|
|
const Queue = require('yocto-queue');
|
|
|
|
const pLimit = concurrency => {
|
|
if (!((Number.isInteger(concurrency) || concurrency === Infinity) && concurrency > 0)) {
|
|
throw new TypeError('Expected `concurrency` to be a number from 1 and up');
|
|
}
|
|
|
|
const queue = new Queue();
|
|
let activeCount = 0;
|
|
|
|
const next = () => {
|
|
activeCount--;
|
|
|
|
if (queue.size > 0) {
|
|
queue.dequeue()();
|
|
}
|
|
};
|
|
|
|
const run = async (fn, resolve, ...args) => {
|
|
activeCount++;
|
|
|
|
const result = (async () => fn(...args))();
|
|
|
|
resolve(result);
|
|
|
|
try {
|
|
await result;
|
|
} catch {}
|
|
|
|
next();
|
|
};
|
|
|
|
const enqueue = (fn, resolve, ...args) => {
|
|
queue.enqueue(run.bind(null, fn, resolve, ...args));
|
|
|
|
(async () => {
|
|
// This function needs to wait until the next microtask before comparing
|
|
// `activeCount` to `concurrency`, because `activeCount` is updated asynchronously
|
|
// when the run function is dequeued and called. The comparison in the if-statement
|
|
// needs to happen asynchronously as well to get an up-to-date value for `activeCount`.
|
|
await Promise.resolve();
|
|
|
|
if (activeCount < concurrency && queue.size > 0) {
|
|
queue.dequeue()();
|
|
}
|
|
})();
|
|
};
|
|
|
|
const generator = (fn, ...args) => new Promise(resolve => {
|
|
enqueue(fn, resolve, ...args);
|
|
});
|
|
|
|
Object.defineProperties(generator, {
|
|
activeCount: {
|
|
get: () => activeCount
|
|
},
|
|
pendingCount: {
|
|
get: () => queue.size
|
|
},
|
|
clearQueue: {
|
|
value: () => {
|
|
queue.clear();
|
|
}
|
|
}
|
|
});
|
|
|
|
return generator;
|
|
};
|
|
|
|
module.exports = pLimit;
|