前端学习（1423）：ajax错误处理

ajax.js

// 引用expess框架
const express = require('express');
// 处理路径
const path = require('path');const bodyParser = require('body-parser');// 创建网站服务器
const app = express();
app.use(bodyParser.json());
app.get('/first', (req, res) => {res.send('hello geyao')
})
app.get('/responsdate', (req, res) => {res.send({ "name": "geyao" })
})
app.post('/post', (req, res) => {res.send(req.body);
})
app.get('/get', (req, res) => {res.send(req.query);
})
app.post('/json', (req, res) => {res.send(req.body);
})
app.get('/readystate', (req, res) => {res.send('hello');
})
app.get('/error', (req, res) => {res.status(400).send('not ok');
})app.use(express.static(path.join(__dirname)));
// 监听端口
app.listen(3000);
console.log('网站服务器启动成功, 请访问localhost')

ajax6.html

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head><body><button id="btn">发送ajax请求</button><script>var xhr = new XMLHttpRequest();xhr.open('get', 'http://localhost:3000/error');xhr.onreadystatechange = function() {//if (xhr.readyState == 4) {//属性获取状态码console.log(xhr.responseText);console.log(xhr.status);if (xhr.status == 400) {console.log('请求出错');} else if (xhr.readyState == 404) {console.log('地址错误');}}xhr.onerror = function() {console.log('网络中断，无法发送ajax请求')}}xhr.send();</script>
</body></html>

运行结果