promise-limit2 ​

描述 ​

const request1 = () => new Promise((resolve, reject) => { setTimeout(() => { resolve(1); }, 1000); });

const request2 = () => new Promise((resolve, reject) => { setTimeout(() => { resolve(2); }, 500); });

const request3 = () => new Promise((resolve, reject) => { setTimeout(() => { resolve(3); }, 300); });

const request4 = () => new Promise((resolve, reject) => { setTimeout(() => { resolve(4); }, 400); });

function scheduler(max) { const queue = []; let running = 0;

function runNextRequest() { if (running >= max || queue.length === 0) { return; }

running++;
const nextRequest = queue.shift();
nextRequest()
  .then((result) => {
    console.log(result);
  })
  .catch((error) => {
    console.error(error);
  })
  .finally(() => {
    running--;
    runNextRequest();
  });

}

return function addRequest(request) { queue.push(request); runNextRequest(); }; }

const addRequest = scheduler(2); addRequest(request1).then((res) => { console.log(res); }); addRequest(request2).then((res) => { console.log(res); }); addRequest(request3).then((res) => { console.log(res); }); addRequest(request4).then((res) => { console.log(res); });

控制并发

题解 ​