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promise使用

news 2025/9/21 14:30:17

1.获取promise的返回结果的正确写法：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>
<script   type="text/javascript">function foo() {return new Promise((resolve, reject) => {resolve('hello world!')});}p = foo()
p.then(result => console.log(result)) // "hello world!"</script></body>
</html>

2.promise发送ajax请求并获取到返回值

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<title>promise-ajax</title>
</head>
<body>
<script type="text/javascript">function foo(url) {return new Promise((resolve, reject) => {$.ajax({url,success(data){resolve(data);},error(err){reject(err);}});});}const url = 'http://localhost:30000/test/say';
p = foo(url)
p.then(result => console.log(result)) // "hello world!"</script></body>
</html>

3.在promise中使用fetch发送请求并获取返回结果

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<title>promise-ajax</title>
</head>
<body>
<script type="text/javascript">function foo(url) {return new Promise((resolve, reject) => {fetch(url).then(response => response.text()).then(data => {debugger;if (data.code === 404) {reject('请求异常：' + data.msg);} else {resolve(data);}}).catch(err => {reject('请求异常：' + err);});});}const url = 'http://localhost:30000/test/say';
p = foo(url)
p.then(result => console.log(result)) // "hello world!"
</script></body>
</html>