Async n承诺从快捷方式改变

Question

我有一个我在一个例子中找到的代码，它都是快捷方式：

async function test1(){
    const p = await new Promise(resolve => setTimeout(resolve, 2000)).then(()=>'test1');
    console.log('Completed test1');
    return p;
}

我想删除setTimeout而不是非快捷方式，所以我可以添加多个命令，除了超时之外还做其他事情......

例如：

async function test1(){
    const p = await new Promise(resolve => setTimeout(resolve) => {
    // line here
    // another one etc
}

如何更改上面的代码？

Answer 1

async function test1(){
    const p = await new Promise(resolve => setTimeout(resolve, 2000)).then(()=>'test1');
    console.log('Completed test1');
    return p;
}

我想你还没有完全理解这段代码。 setTimeout不是捷径。 new Promise(resolve => setTimeout(resolve, 2000))用于创建一个在2000毫秒后解析的承诺。您可以将其视为API调用，它将在2000ms后调用回调

让我们打破这段代码：

// A function test1 which is defined async sow you can use await inside it
async function test1(){
    // You can await for promises.
    //  As explained await new Promise(resolve => setTimeout(resolve, 2000)) 
    // is just a promise resolving after 2000ms
    const p = await new Promise(resolve => setTimeout(resolve, 2000))
     // .then block will run after promise gets resolved
     // p will bcome test1
    .then(()=>'test1');
    console.log('Completed test1');
    return p;
}

如果你想有条件地解决诺言并做一些计算，你可以在setTimeout函数中做到这一点：

await new Promise(resolve => 
    setTimeout(()=>{
        if('Some consition'){
            resolve('some value')
        }
        else{
            resolve('some other value')
        }
    }, 2000)
)