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模拟Async.html
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模拟Async.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>TEST</title>
<style>
body {
padding: 16px 32px;
}
pre {
padding: 16px;
line-height: 1.5;
background-color: #f5f5f5;
}
</style>
</head>
<body>
<H3> 实现一个 async </H3>
<pre>
</pre>
</body>
<script>
function async(generator) {
return new Promise(function (resolve, reject) {
const it = generator();
function step(next) {
let result;
try {
result = next();
console.log(result)
} catch (e) {
return reject(e);
}
if (result.done) {
return resolve(result.value);
}
Promise.resolve(result.value).then(
function (v) {
step(function () {
return it.next(v);
});
},
function (e) {
step(function () {
return it.throw(e);
});
},
);
}
step(function () {
return it.next(undefined);
});
});
}
const promise = new Promise((resolve) => {
setTimeout(() => {
resolve('1111111')
}, 1000);
})
const sleep = function (time, value) {
return new Promise((resolve) => {
setTimeout(() => {
resolve(value)
}, time);
})
}
function append(value) {
console.log(value)
const el = document.createElement('div')
el.innerHTML = value
document.body.appendChild(el)
}
async(function* () {
try {
const a = yield promise;
append(a)
const b = yield sleep(1500, 2222222);
append(b)
const c = yield sleep(500, 3333333);
append(c)
throw new Error('xxxxx')
} catch (e) {
console.log("内部捕获", e);
}
});
</script>
</html>