parallelPromise.js

// this code pauses and executes one after another
function five() {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve("i am after five seconds"), 5000);
  });
}

function three() {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve("i am after three seconds"), 3000);
  });
}

async function test() {
  let fiveData = await five();
  let threeData = await three();
  console.log(fiveData);
  console.log(threeData);
}

test();



// this code executes in parallel
function five() {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve("i am after 5 seconds"), 5000);
  });
}

function three() {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve("i am after 3 seconds"), 3000);
  });
}

function one() {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve("i am after 1 second"), 1000);
  });
}

async function test() {
  [fiveData, threeData, oneData] = await Promise.all([five(), three(), one()]);
  console.log(fiveData);
  console.log(threeData);
  console.log(oneData);
}

test();