イベントloop原理、マクロタスク、nodeとブラウザがloopを実現する時の違い

console.log("script start");

new Promise(function (resolve) {
  console.log("promise1");
  resolve();
}).then(function () {
  console.log("promise1-then");
});

setTimeout(function () {
  console.log("settimeout1");
}, 0);

async function async1() {
  console.log("async1 start");
  let resulet = await async2();
  console.log(resulet);
  console.log("async1 end");
}

async function async2() {
  console.log('async2');
  return "async2 return"
}

setTimeout(function () {
  console.log("settimeout2");
}, 0);

async1();

new Promise(function (resolve) {
  console.log("promise2");
  resolve();
}).then(function () {
  console.log("promise2-then");
});

console.log('script end');

script start
promise1
async1 start
async2
promise2
script end
promise1-then
promise2-then
async2 return
async1 end
settimeout1
settimeout2

script start
VM7991:4 promise1
VM7991:15 async1 start
VM7991:22 async2
VM7991:33 promise2
VM7991:39 script end
VM7991:7 promise1-then
VM7991:17 async2 return
VM7991:18 async1 end
VM7991:36 promise2-then
undefined
VM7991:11 settimeout1
VM7991:27 settimeout2