JavaScriptCodeSnippets/ParallelAsync.js at master · rnagasudhakar/JavaScriptCodeSnippets · GitHub

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// takes async function as input and invoke callback after async function  is completed

const p1 = new Promise((resolve) => {
  setTimeout(() => {
    resolve("P1");
  }, 1000);
});

const p2 = new Promise((resolve) => {
  setTimeout(() => {
    resolve("P2");
  }, 2000);
});

const p3 = new Promise((resolve) => {
  setTimeout(() => {
    resolve("P3");
  }, 100);
});

const callback = () => {
  console.log("hello");
};

const p4 = [p1, p2, p3];

// or simply use Promise.all
function executeParallel(p4, callback) {
  let count = 0;
  p4.forEach((promise) => {
    promise.then((val) => {
      count++;
      console.log(val);
      if (count === p4.length) {
        callback();
      }
    });
  });
}

executeParallel(p4, callback);