Promise2.js

const test = new Promise((resolve, reject) => {
    setTimeout(()=>{
        console.log("4秒経過");
        resolve(3000);
    },4000)
});

test
.then((sec) => new Promise((resolve) => setTimeout(() => { console.log("7秒経過");resolve(2000); },sec)))　　//sec=3000
.then((sec) => new Promise((resolve) => setTimeout(() => { console.log("9秒経過");resolve(1000); },sec)))　　//sec=2000
.then((sec) => new Promise((resolve) => setTimeout(() => { console.log("10秒経過");resolve(); },sec)))　　　　　　　　//sec=1000