我通過 MDN 文檔找到了以下代碼。var resolveAfter2Seconds = function() {  console.log("starting slow promise");  return new Promise(resolve => {    setTimeout(function() {      resolve(20);      console.log("slow promise is done");    }, 2000);  });};var resolveAfter1Second = function() {  console.log("starting fast promise");  return new Promise(resolve => {    setTimeout(function() {      resolve(10);      console.log("fast promise is done");    }, 1000);  });};var parallel = function() {  console.log('==PARALLEL with Promise.then==');  resolveAfter2Seconds().then((message)=>console.log(message));  resolveAfter1Second().then((message)=>console.log(message));}作為執(zhí)行的結(jié)果，我認(rèn)為每個(gè) Promise 都將是沒有順序保證的并行執(zhí)行。但是我寫了下面的代碼，似乎可以保證順序。const promiseFunction1 = () => {    return new Promise((resolve) => {        let result = 0;        for (let i = 0; i < 1000000000; i++) {            result += 1;        }        resolve(result);    })}const promiseFunction2 = () => {    return new Promise((resolve) => {        let result = 0;        for (let i = 0; i < 10; i++) {            result += 1;        }        resolve(result);    })}const parallel = () => {    promiseFunction1()        .then(res => console.log(res));    promiseFunction2()        .then(res => console.log(res));}這兩個(gè)代碼有什么區(qū)別？