/*** resolve 异步操作成功时调用的方法，并将异步操作的结果作为参数传递出去* reject 异步操作失败时调用的方法，并将报错传递出去*/
var promise = new Promise(function(resolve, reject) {var isSuccess = true // 异步操作是否成功if (isSuccess) {resolve(data)} else {reject(error)}
})

promise.then(function() {    // 异步操作成功的处理，resolve状态
}, function() {  // 异步操作失败的处理，reject状态})

var timeout = function(ms) {var data = {list: Array(0),msg: 'success',status: 200}return new Promise(function(resolve, reject) {setTimeout(resolve, ms, data)})
}
timeout(1000).then(function(data) {console.log(data)
}, function(error) {console.log(error)
})

function loadImageAsync(src) {return new Promise(function(resolve, reject) {var image = new Image()image.src = srcimage.onload = function() {resolve(image)}image.onerror = function() {reject(new Error(`加载图片失败，url：${url}`))}})
}var url = 'http://n.sinaimg.cn/ent/transform/250/w160h90/20190226/jjhJ-htptaqe5318645.jpg'
loadImageAsync(url).then((image) => {document.body.append(image)
}, (err) => {console.log(err)
})

function timeout(ms) {return new Promise(function(resolve, reject) {setTimeout(() => {resolve()}, ms)})
}async function asyncPrint(ms) {await timeout(ms)console.log(`过去了${ms}毫秒，输出此语句`)
}asyncPrint(1000)

async function f() {return 'hello'
}f().then((data) => {console.log(data) // ‘hello’
})

async function f() {throw new Error('出错了')
}f().then((data) => {console.log('resolve data:', data)
}).catch((err) => {console.log('reject error:', err)
})

f().then(data => console.log(data),err => console.log(err)
)

async function main() {try {const val1 = await firstStep();const val2 = await secondStep(val1);const val3 = await thirdStep(val1, val2);console.log('Final: ', val3);}catch (err) {console.error(err);}
}