ilustrar:
- Para utilizar el objeto fuera de la función
let xhr, constse informará un error después de la modificación.
xhr.abort();Una solicitud enviada se puede cancelar a través de
código de interfaz
<html>
<head>
<meta http-equiv="Access-Control-Allow-Origin" content="*" />
</head>
<body>
<button>点击请求</button>
<button>取消请求</button>
<div id="content" style="width: 300px;height:200px;border:1px solid;"></div>
</body>
<script>
const btn = document.getElementsByTagName('button');
const content = document.getElementById('content');
let xhr = null
btn[0].onclick = function(){
xhr = new XMLHttpRequest();
xhr.open('GET', 'http://127.0.0.1:8000/delay');
xhr.send('a=200&b=300');
xhr.onreadystatechange = function(){
if(xhr.readyState === 4){
if(xhr.status >= 200 && xhr.status < 300){
content.innerHTML = xhr.response;
}
}
}
}
btn[1].onclick = function(){
xhr.abort();
content.innerHTML = '';
}
</script>
</html>
jssecuencia de comandos de fondo
const express = require('express');
const app = express()
app.get('/server', (Request, Response)=>{
Response.setHeader('Access-Control-Allow-Origin', '*')
Response.send('Hello Ajax')
})
app.get('/delay', (Request, Response)=>{
Response.setHeader('Access-Control-Allow-Origin', '*')
setTimeout(()=>{
Response.send('Hello Ajax')
}, 3000)
})
app.get('/ie', (Request, Response)=>{
Response.setHeader('Access-Control-Allow-Origin', '*')
Response.send('Hello IE')
})
app.post('/server', (Request, Response)=>{
Response.setHeader('Access-Control-Allow-Origin', '*')
Response.send('Hello Ajax-4')
})
app.listen(8000, ()=>{
console.log('8000 running meproject express')
})