javascript - Promise 如何解决但结果未定义？

Question

如果 promise 已解决，输出中的 repos 是未定义的。

代码的输出是:

reading from database........

hello

repos are : undefined

reading from repository

getuser(1)
                .then( result =>{console.log('hello');getRepository(result.username)})
                .then( repos =>console.log('repos are :',repos));

相关的异步函数有

function getuser(id){
return new Promise((resolve,reject)=>{
    setTimeout(() => {
        console.log('reading from database........')
        resolve({id:id , username:"sunil"});
    }, 5000);
});

function getRepository(username){
return new Promise((resolve,reject)=>{
    setTimeout(()=>{
        console.log('reading from repository')
        resolve(['repos1','repos2','repos3']);  
    }
     ,3000);
})

Answer 1

你的第一个 .then 没有返回任何东西，所以它立即解析。更改为 return getRepository(...。