image-20211217112631141

  • 因为我们仅仅需要记住几个 MicroTask 即可，排除法！别的都是 MacroTask。MicroTask 包括：Process.nextTick、Promise.then catch finally(注意我不是说 Promise)、MutationObserver。
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console.log(1);
setTimeout(function () {
  console.log(2);
  process.nextTick(function () {
    console.log(3);
  });
  new Promise(function (resolve) {
    console.log(4);
    resolve();
  }).then(function () {
    console.log(5);
  });
});
process.nextTick(function () {
  console.log(6);
});
new Promise(function (resolve) {
  console.log(7);
  resolve();
}).then(function () {
  console.log(8);
});
setTimeout(function () {
  console.log(9);
  process.nextTick(function () {
    console.log(10);
  });
  new Promise(function (resolve) {
    console.log(11);
    resolve();
  }).then(function () {
    console.log(12);
  });
});
// 1,7,6,8,2,4,3,5,9,11,10,12
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setImmediate(function () {
  console.log(1);
}, 0);
setTimeout(function () {
  console.log(2);
}, 0);
new Promise(function (resolve) {
  console.log(3);
  resolve();
  console.log(4);
}).then(function () {
  console.log(5);
});
console.log(6);
process.nextTick(function () {
  console.log(7);
});
console.log(8);
// 3 4 6 8 7 5 1 2
// micro-task   优先级 process.nextTick 高于 Promise.then
// macro-task   浏览器内核下，优先级 setImmediate 高于 setTimeout