Javascript 承諾，所有的 .then 同時執行

Question

此時.then之后的所有console.log，同時執行。 我希望每個 .then 等待前一個，我該怎么做？

function doIt(sentence) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(console.log(sentence))
        }, 2000)
    })
}

doIt('Place order')
    .then(() => setTimeout(() => { console.log('Cut the fruit') }, 2000))
    .then(() => setTimeout(() => { console.log('Add water and ice') }, 2000))
    .then(() => setTimeout(() => { console.log('Start the machine') }, 2000))
    .then(() => setTimeout(() => { console.log('Select topping') }, 2000))
    .then(() => setTimeout(() => { console.log('Serve the ice cream') }, 2000))

Answer 1

你必須創建一個承諾鏈。

 function doIt(sentence) { return new Promise((resolve, reject) => { setTimeout(() => resolve(console.log(sentence)), 2000); }); } doIt("Place order") .then(() => doIt("Cut the fruit")) .then(() => doIt("Add water and ice")) .then(() => doIt("Start the machine")) .then(() => doIt("Select topping")) .then(() => doIt("Serve the ice cream"));