async/await 的特点:
可以让异步逻辑用同步写法实现
最底层的await返回需要是Promise对象
可以通过多层 async function 的同步写法代替传统的callback嵌套
function getSyncTime() {
return new Promise((resolve, reject) => {
try {
let startTime = new Date().getTime()
setTimeout(() => {
let endTime = new Date().getTime()
let data = endTime - startTime
resolve(data)
}, 500)
} catch (err) {
reject(err)
}
})
}
async function getSyncData() {
let time = await getSyncTime()
let data = `endTime - startTime - ${time}`
return data
}
async function getData() {
let data = await getSyncData()
console.log( data )
}
getData();