Ajax 获取进度和中断请求

HTML加入一些内容方便看效果和做交互：

<div>
  <p>当前传输进度：<span id="progress">0%</span></p>
  <button id="send">发送</button>
  <button id="btn">中断</button>
</div>

JavaScript 核心代码：

// 发送请求
    document.getElementById('send').addEventListener('click', function () {
      const xhr = new XMLHttpRequest()
      xhr.open('GET', 'http://localhost:9001/test')
      xhr.onreadystatechange = function () {
        if (xhr.readyState === 4 && xhr.status === 200) {
          console.log(xhr.responseText)
        }
      }

      // 获取进度
      xhr.addEventListener('progress', function (e) {
        console.log(e)
        const percent = (e.loaded / e.total) * 100
        document.getElementById('progress').textContent = percent.toFixed(2) + '%'
      })

      // 点击按钮中断请求
      document.getElementById('btn').addEventListener('click', function () {
        console.log('中断请求')
        xhr.abort()
      })

      xhr.send()
    })

这里我自己弄了个简单的node服务器做测试：

const express = require('express')
const app = express()

//创建get请求
app.get('/test', (req, res) => {
  res.setHeader('Content-Type', 'application/json;charset=utf-8')
  res.setHeader('Access-Control-Allow-Origin', '*')

  // 读取txt文件
  const fs = require('fs')
  const data = fs.readFileSync('resData.txt', 'utf-8')

  res.json({
    code: 200,
    message: "请求成功",
    data
  })

})
//端口号9001
app.listen(9001)
console.log('server is running at http://localhost:9001')