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JS  XML和Fetch

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1.HTTP 简介

HTTP/0.9 ( 1991 )

HTTP/1.0 (1996 )

HTTP/1.1(1997)

HTTP1.x请求报文

HTTP1.x响应报文

常用状态码

header请求头

名字说明示例
Accept告知(服务器)客户端可以处理的内容类型text/html, application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Aaccept-Encoding客户端能够理解的内容编码方式gzip, deflate
Accept-Language客户端可以理解的语言zh-CN,zh;q=0.9,en;q=0.8
Cache-Control表示浏览器的缓存方式Cache-Control: max-age = xxx
cookiecookie信息 
Connection是否是长连接keep-live
Content-Type实际发送的数据类型content-type:application/x-www-form
Host要发送到的服务器主机名和端口号www.baidu.com
User-Agent用户代理。包含应用类型、操作系统、软件开发商以及版本号等 
Referer当前请求的来源页面的地址 

header响应头

名字说明示例
Date服务器的响应的日期和时间 
Connection是否会关闭网络连接Connection: keep-alive
Keep-Alive空闲连接需要保持打开状态Keep-Alive: timeout=5, max=10的最小时长和最大请求数( Connection设置为“keep-alive”才有意义)Keep-Alive: timeout=5, max=10空闲5秒,最多接收10次请求就断开。
Content-Encoding内容编码方式Content-Encoding: gzip
Content-Length报文中实体主体的字节大小content-Length: 1963
Content-Type内容的内容类型Content-Type: text/html; charset=utf-8
Server服务器所用到的软件相关信息Server: openresty
基于NGINX的可伸缩的Web平台
Set-Cookie向客户端发送cookieSet-Cookie:
imooc_isnew=2; expires=Thu, 02-Mar-202312:3242 GMT; Max-Age=31536000; path=/;
domain=.baidu.com

Content-Type

1.application/x-www-form-urlencoded

<body>
    <button type="button" id="btnSend">发送请求</button>
    <div>
        <div>结果:</div>
        <div id="result"></div>
    </div>
    <script>
        btnSend.onclick = fetchByUrlencoded;

        function fetchByUrlencoded() {
            // 对中文还能自行编码
            // const params = new URLSearchParams({
            //     name: 'yunmu',
            //     age: 18
            // });
            fetch("/urlencoded", {
                method: "POST",
                headers: {
                    "Content-Type": "application/x-www-form-urlencoded",
                },
                body: "name=yunmu&age=18",
                // body: params.toString()
            })
                .then((res) => res.json())
                .then((res) => {
                console.log("收到结果:", res);
                result.innerHTML = JSON.stringify(res);
            });
        }
    </script>
</body>

2.multipart/form-data

<body>
    <div>结果:</div>
    <div id="result"></div>

    <div>表单提交</div>
    <form action="/multipart" method="post" enctype="multipart/form-data">
      <input type="text" name="name" value="tom" />

      <input type="text" name="age" value="18" />

      <button type="submit">提交表单</button>
    </form>
    <hr />
    <div>代码提交:</div>
    <button type="button" id="btnSend">发送请求</button>
    <script>
      btnSend.onclick = fetchByMultipart;

      function fetchByMultipart() {
        const formData = new FormData();
        formData.append("name", "yunmu");
        formData.append("age", 18);

        fetch("/multipart", {
          method: "POST",
          // 不要设置 content-type
          // headers: {
          //     "Content-Type": "multipart/form-data",
          // },
          body: formData,
        })
          .then((res) => res.json())
          .then((res) => {
            console.log("收到结果:", res);
            result.innerHTML = JSON.stringify(res);
          });
      }
    </script>
  </body>

3.application/json

<body>
    <button type="button" id="btnSend">发送请求</button>
    <div>
        <div>结果:</div>
        <div id="result"></div>
    </div>

    <script>
        btnSend.onclick = fetchByJSON;

        function fetchByJSON() {
            fetch("/json", {
                method: "POST",
                headers: {
                    "Content-Type": "application/json",
                },
                body: JSON.stringify({ name: "yunmu", age: 18 }),
            })
                .then((res) => {
                console.log("返回的content-type:", res.headers.get("Content-Type"));
                return res;
            })
                .then((res) => res.json())
                .then((res) => {
                console.log("收到结果:", res);
                result.innerHTML = JSON.stringify(res);
            });
        }
    </script>
</body>

服务端代码:

const express = require("express");
const path = require("path");
const multer = require("multer");

const server = express();

server.use(
  express.urlencoded({
    extended: true,
  })
);

server.use(express.json());

server.use(express.static(path.join(__dirname, "./static")));

server.use("/urlencoded", function (req, res) {
  console.log("收到请求(urlencoded)");
  console.log("body:", req.body);
  res.json({
    code: 10000,
    data: req.body,
  });
});

server.use("/multipart", multer().none(), function (req, res) {
  console.log("收到请求(multipart)");
  console.log("body:", req.body);
  res.json({
    code: 10000,
    data: req.body,
  });
});
server.use("/json", multer().none(), function (req, res) {
  console.log("收到请求(json)");
  console.log("body:", req.body);
  res.json({
    code: 10000,
    data: req.body,
  });
});
server.listen(3000, function () {
  console.log("listening at port 3000");
});

https

HTTP2

HTTP3

2.Ajax

XHR

基本使用:

<body>
    <div>测试ajax 界面</div>
    <button id="ajaxBtn">AjAX局部刷新</button>
    <div class="ajax-change" id="responseDiv">change区域</div>
    <script>
        function test() {
            //1. 创建实例对象
            const xhrObj = new XMLHttpRequest();

            //注册readystatechange回调监听
            xhrObj.onreadystatechange = function () {
                //readyState==4 && status=200 代表请求成功
                if (xhrObj.readyState == 4 && xhrObj.status == 200) {
                    //局部刷新文本
                    document.getElementById("responseDiv").innerHTML = xhrObj.responseText;
                }
            };

            //请求错误回调
            xhrObj.onerror = function () {
                console.log("-------onerror-------:");
            };

            //请求成功完成回调
            xhrObj.onload = function () {
                console.log("-------onload-------:", xhrObj.responseText);
            };

            //请求开始回调
            xhrObj.onloadstart = function () {
                console.log("-------onloadstart-------");
            };

            //请求完成回调,不论请求成功与否
            xhrObj.onloadend = function () {
                console.log("-------onloadend-------");
            };

            //设置请求地址,true 异步请求,false:同步请求,
            xhrObj.open("post", "http://127.0.0.1:3000/xhr", true);
            //设置请求携带header
            xhrObj.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
            //发送请求数据
            xhrObj.send("xhr=1");
        }

        document.getElementById("ajaxBtn").addEventListener("click", function () {
            test();
        });
    </script>
</body>

服务端代码:

import http from "http";
import bodyParser from "body-parser";
import express from "express";
import createError from "http-errors";
// const multiparty = require('multiparty');

const port = 3000;

const app = express();

app.use(bodyParser.urlencoded({ extended: true }));
const server = http.createServer(app);

//设置跨域访问
app.use(function (req, res, next) {
  //设置允许跨域的域名,*代表允许任意域名跨域
  //"*"
  res.header("Access-Control-Allow-Origin", req.headers.origin);
  //允许携带cookie
  res.header("Access-Control-Allow-Credentials", "true");
  //允许的header类型
  res.header("Access-Control-Allow-Headers", [
    "X-PINGOTHER",
    "content-type",
    "Origin",
    "X-Requested-With",
  ]);
  //跨域允许的请求方式
  res.header("Access-Control-Allow-Methods", "DELETE,PUT,POST,GET,OPTIONS");

  res.header("Access-Control-Max-Age", `${20}`);
  if (req.method.toLowerCase() == "options") res.send(200);
  //让options尝试请求快速结束
  else next();
});

app.post("/xhr", async (_req, _res) => {
  console.log("xhr: 收到请求");

  await sleep(2 * 1000);

  _res.json({
    code: 10000,
  });
});

function sleep(time: number) {
  return new Promise((resolve) => setTimeout(resolve, time));
}

app.get("/fetch", async (_req, res) => {
  console.log("fetch:收到请求", _req.url);
  await sleep(10 * 1000);
  return res.json({
    code: 10000,
  });
});

app.get("/test1", (_req, res) => {
  res.send("test1");
});

app.get("/test2", (_req, res) => {
  res.send("test2");
});

app.get("/timeout", async (_req, res) => {
  await sleep(12 * 1000);
  res.send("test2");
});

app.get("/test4", async (_req, res) => {
  console.log("收到请求=test4=", _req.url);
  // res.send('hello')
  await sleep(30000);
  return res.json({
    REV: true,
    DATA: {
      msg: "成功",
    },
  });
});

server.listen(port, () => {
  console.log("监听端口:", port);
});

// catch 404 and forward to error handler
app.use((_req: express.Request, _res: express.Response, next: express.NextFunction) => {
  const error = createError(404);
  next(error);
});

process.on("unhandledRejection", (reason: {} | null | undefined, p: Promise<any>) => {
  console.error("自定义错误 Unhandled Rejection at:", p, "reason:", reason);
  // application specific logging, throwing an error, or other logic here
});

缺点

Fetch

image

优点

基本使用:

<script>
    // get
    fetch("http://127.0.0.1:3000/test1")
        .then((response) => response.text())
        .then((text) => console.log("获取到的数据对象:", text))
        .catch((err) => console.log("Request Failed", err));

    //post
    fetch("http://127.0.0.1:3000/report", {
        method: "POST",
        headers: {
            "Content-Type": "application/x-www-form-urlencoded;",
        },
        body: "report=2",
        mode: "cors", //设置跨域
    })
        .then((response) => response.json())
        .then((json) => console.log("post 获取到的数据对象:", json))
        .catch((err) => console.log("Request Failed", err));
</script>

拦截3xx重定向

 <body>
    <div>
      <button id="btnXhr">XHR</button>
      <button id="btnFetch">Fetch</button>
    </div>

    <script>
      btnXhr.onclick = xhr30x;
      btnFetch.onclick = fetch30x;

      function fetch30x() {
        fetch("http://www.baidu.com", { redirect: "error" }).catch((err) =>
          console.log("err:", err)
        );
      }
      function xhr30x() {
        const xhrObj = new XMLHttpRequest();
        xhrObj.onreadystatechange = function () {
          console.log("xhrObj.status==", xhrObj.status);
        };
        xhrObj.open("get", "http://www.baidu.com", true);
        //设置请求携带header
        xhrObj.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        //发送请求数据
        xhrObj.send("xhr=1");

        xhrObj.onerror = function () {
          console.log("-------onerror-------:");
        };
      }
    </script>
  </body>

缺点

XML请求取消

Fetch请求取消

AbortController对象的abort()

<body>
    <div>测试fetch 界面</div>
    <button id="btnSend">发送请求</button>
    <button id="btnCancel">取消请求</button>
    <script>
        const controller = new AbortController();
        const signal = controller.signal;

        btnSend.onclick = function sendFetch(test) {
            fetch("http://127.0.0.1:3000/fetch", { signal })
                .then((response) => {
                return response.text();
            })
                .then((text) => {
                console.log(text);
            });
        };

        btnCancel.onclick = function () {
            console.log("取消请求");
            controller.abort();
        };
    </script>
</body>

Axios请求取消

const controller = new AbortController();
const signal = controller.signal;

axios.get("/foo", {
    signal,
}).then(() => {});

// 取消请求
controller.abort();

XML获取 progress

 <body>
    <div>测试ajax 界面</div>
    <button id="ajaxBtn">AjAX局部刷新</button>
    <script>
      function test() {
        // 创建实例对象
        const xhrObj = new XMLHttpRequest();
        xhrObj.responseType = "blob";
        //onprogress
        xhrObj.onprogress = function (event) {
          console.log(
            "total:",
            event.total,
            "progress:",
            event.loaded,
            "%:",
            (event.loaded / event.total) * 100 + "%"
          );
          if (event.lengthComputable) {
            console.log("获取完毕");
          }
        };

        xhrObj.open("get", "./test.mp4", true);

        //发送请求数据
        xhrObj.send();

        //请求成功完成后下载
        // xhrObj.onload = function (oEvent) {
        //   console.log(oEvent, "oEvent===");
        //   console.log(xhrObj.status, "status===");
        //   console.log(xhrObj.response, "response===");
        //   if (xhrObj.readyState === 4 && xhrObj.status === 200) {
        //     const blob = new Blob([xhrObj.response]);
        //     const video = URL.createObjectURL(blob);
        //     const link = document.createElement("a");
        //     link.href = video;
        //     link.download = "test.mp4";
        //     link.click();
        //   }
        // };
      }

      document.getElementById("ajaxBtn").addEventListener("click", function () {
        test();
      });
    </script>
  </body>

Fetch获取Progress

<body>
    <script>
      let progress = 0;
      let contentLength = 0;

      fetch("./test.mp4")
        .then((response) => {
          // 通过响应头获取文件大小
          contentLength = response.headers.get("Content-Length");
          const reader = response.body.getReader();

          return reader.read().then(function processResult(result) {
            if (result.done) {
              console.log("请求完毕");
              return;
            }

            progress += result.value.byteLength;
            console.log(
              "total:",
              contentLength,
              "progress:",
              progress,
              "%:",
              (progress / contentLength) * 100 + "%"
            );

            return reader.read().then(processResult);
          });
        })
        .catch((err) => console.log("Request Failed", err));
    </script>
  </body>

XML超时

<body>
    <div>测试ajax 界面</div>
    <button id="ajaxBtn">发起超时请求</button>
    <div class="ajax-change" id="responseDiv">change区域</div>
    <script>
      function test() {
        //1. 创建实例对象
        const xhrObj = new XMLHttpRequest();

        //请求错误回调
        xhrObj.onerror = function () {
          console.log("-------onerror-------:");
        };

        //请求完成回调,不论请求成功与否
        xhrObj.onloadend = function () {
          console.log("-------onloadend-------");
        };

        //超时监听
        xhrObj.ontimeout = function () {
          console.error("The request timed out.");
          document.getElementById("responseDiv").innerHTML = "The request timed out";
        };
        //设置网络超时时间
        xhrObj.timeout = 5 * 1000;

        xhrObj.open("GET", "http://127.0.0.1:3000/timeout", true);
        //发送请求数据
        xhrObj.send();
      }

      document.getElementById("ajaxBtn").addEventListener("click", function () {
        test();
      });
    </script>
  </body>

Fetch超时

<body>
    <div>fetch 不支持超时</div>
    <button id="ajaxBtn">发起超时请求</button>
    <div class="ajax-change" id="responseDiv">change区域</div>
    <script>
      const oldFetch = fetch;
      window.fetch = function (input, opts) {
        return new Promise(function (resolve, reject) {
          //开启超时
          const timeoutId = setTimeout(function () {
            reject(new Error("fetch timeout"));
          }, opts.timeout);
          oldFetch(input, opts).then(
            (res) => {
              //清除超时
              clearTimeout(timeoutId);
              resolve(res);
            },
            (err) => {
              //清除超时
              clearTimeout(timeoutId);
              reject(err);
            }
          );
        });
      };

      function test() {
        // get
        fetch("http://127.0.0.1:3000/timeout", { timeout: 5 * 1000 })
          .then((response) => response.text())
          .then((text) => console.log("获取到的数据对象:", text))
          .catch((err) => console.error("Request Failed", err));
      }

      document.getElementById("ajaxBtn").addEventListener("click", function () {
        test();
      });
    </script>
  </body>

Fetch同源携带Cookie

<body>
    <button id="ajaxBtn">xhr 携带cookie</button>
    <script>
      function test() {
        //2018年以后 默认值从 {"credentials":"omit"}  修改为 {"credentials":"same-origin"}
        fetch("./a.png")
          .then((response) => response.text())
          .then((text) => console.log("获取到的数据对象:", text))
          .catch((err) => console.log("Request Failed", err));
      }

      document.getElementById("ajaxBtn").addEventListener("click", function () {
        test();
      });
    </script>
  </body>

Fetch错误码

 <body>
    <button id="ajaxBtn">fetch 404错误码</button>
    <script>
      function test() {
        fetch("http://127.0.0.1:3000/test3", {
          credentials: "include",
          mode: "cors",
        })
          .then((response) => {
            console.log("请求成功status:", response.status);
            return response.text();
          })
          .catch((err) => console.log("Request Failed", err));
      }

      document.getElementById("ajaxBtn").addEventListener("click", function () {
        test();
      });
    </script>
  </body>

兼容XHR对象

function getXHR() {
  let xhr = null;
  if (window.XMLHttpRequest) {
    xhr = new XMLHttpRequest();
  } else if (window.ActiveXObject) {
    //遍历IE中不同版本的ActiveX对象
    let version = ["Msxml2", "Microsoft"];
    for (let i = 0; i < version.length; i++) {
      try {
        xhr = new window.ActiveXObject(version[i] + ".XMLHTTP");
        return;
      } catch (e) {
        console.log(e);
      }
    }
  }
  return xhr;
}

3.同源策略和跨域请求

同源策略限制

跨域网络访问

不同源的窗口/文档交流

网络跨域解决方案

1.JSONP

<script>
    function jsonpCallback(data) {
        console.log("我收到的数据了:", data);
    }
</script>
<script src="http://127.0.0.1:3000/jsonp_request?callback=jsonpCallback"></script>
app.get("/jsonp_request", (_req, res) => {
  const params = urlLib.parse(_req.url, true);
  if (params.query && params.query.callback) {
    const str = params.query.callback + "(" + JSON.stringify({ test: "服务端数据" }) + ")";
    res.send(str);
  } else {
    res.send("Hello Yun");
  }
  // 可拿到回调函数的名称
  console.log(params.query.callback);
});

JSONP缺点

2.CORS

简单请求

let whitList = ["http://127.0.0.1:5500"]; //设置白名单
//设置跨域访问
app.use(function (req, res, next) {
  const origin = req.headers.origin as string;
  if (whitList.includes(origin)) {
    //设置允许跨域的域名,*代表允许任意域名跨域
    res.header("Access-Control-Allow-Origin", origin);
    //允许携带凭证
    res.header("Access-Control-Allow-Credentials", "true");
    //允许的header类型
    res.header("Access-Control-Allow-Headers", ["X-PINGOTHER", "content-type", "Origin", "Accept"]);
    //允许浏览器访问的响应头
    res.header("Access-Control-Expose-Headers", "test");
    //跨域允许的请求方式
    res.header("Access-Control-Allow-Methods", "DELETE,PUT,POST,GET,OPTIONS");
    //预检结果保存时间 1小时
    res.header("Access-Control-Max-Age", `${5}`);
    if (req.method.toLowerCase() == "options") {
      res.send(204); //让 options 尝试请求快速结束
      return;
    }
  }
  next();
});

CORS中间件

let whitList = ["http://127.0.0.1:5500"]; //设置白名单

const corsOptions = {
    origin: function (origin, callback) {
        if (whitList.indexOf(origin) !== -1) {
            callback(null, true);
        } else {
            callback(new Error("Not allowed by CORS"));
        }
    },
    credentials: true,
    maxAge: 20,
    allowedHeaders: ["X-PINGOTHER", "content-type", "Origin", "Accept"],
};

app.use(cors(corsOptions));

复杂请求

网络跨域解决方案-正向代理

网络跨域解决方案-反向代理

WebSocket

服务端:

const WebSocket = require("ws");
const server = new WebSocket.Server({ port: 18000 });
server.on("open", function open() {
  console.log("connected");
});
server.on("close", function close() {
  console.log("disconnected");
});
server.on("connection", function connection(ws, req) {
  // 发送欢迎信息给客户端
  ws.send("服务器欢迎你链接");

  ws.on("message", function incoming(message) {
    // 广播消息给所有客户端
    server.clients.forEach(function each(client) {
      if (client.readyState === WebSocket.OPEN) {
        client.send("服务器收到客户端消息 -> " + message);
      }
    });
  });
});

客户端:

<style>
    .txt {
      font-size: 30px;
    }
    .inputBtn {
      font-size: 40px;
    }
  </style>
  <body>
    <form onsubmit="return false;">
      <h1>慕课聊天室:</h1>
      <textarea id="repText" class="txt" style="width: 800px; height: 600px"></textarea>
      <br />
      <input
        class="inputBtn"
        type="text"
        id="myInput"
        name="message"
        style="width: 300px"
        value="Hello world"
      />
      <input
        class="inputBtn"
        type="button"
        id="mySend"
        value="发送消息"
        onclick="send(this.form.message.value)"
      />
    </form>

    <script type="text/javascript">
      let socket;
      const repTextEl = document.getElementById("repText");
      if (window.WebSocket) {
        socket = new WebSocket("ws://127.0.0.1:18000");
        socket.onmessage = function (event) {
          repTextEl.value = repTextEl.value + "\n" + event.data;
        };
        socket.onopen = function (event) {
          repTextEl.value = "webSocket已链接";
        };
        socket.onclose = function (event) {
          repTextEl.value = repTextEl.value + "连接被关闭";
        };
      } else {
        console.log("浏览器不支持webSocket");
      }

      function send(message) {
        if (!window.WebSocket) {
          return;
        }
        if (socket.readyState == WebSocket.OPEN) {
          socket.send(message);
        } else {
          console.log("webSocket还没有开启");
        }
      }
    </script>
  </body>

总结

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