fetch:

      fetch("xxx", {
                method: "post",
        headers: {
          "Content-Type": "application/json",
        },
        body: JSON.stringify({
          name: "Hubot",
          login: "hubot",
        }),
      });

上传文件：

 var formData = new FormData();
      formData.append("file", file);
      console.log(formData.get("file"));
      fetch("http://localhost:3000/blogData/upload", {
        method: "POST",
        body: formData,
      // headers: {
        // //不需要写'Content-Type': 'multipart/form-data',自动是form -data 写了报错！离谱！
        // 'Content-Type': 'multipart/form-data',
        // },
      })
        .then((res) => {
          return res.json();
        })
        .then((res) => {
          console.log(res);
        });

axios:

执行 GET 请求

// 为给定 ID 的 user 创建请求
axios.get('/user?ID=12345')
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

// 上面的请求也可以这样做
axios.get('/user', {
    params: {
      ID: 12345
    }
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

执行 POST 请求

axios.post('/user', {
    firstName: 'Fred',
    lastName: 'Flintstone'
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

执行多个并发请求

function getUserAccount() {
  return axios.get('/user/12345');
}

function getUserPermissions() {
  return axios.get('/user/12345/permissions');
}

axios.all([getUserAccount(), getUserPermissions()])
  .then(axios.spread(function (acct, perms) {
    // 两个请求现在都执行完成
  }));

添加heads:

        axios
          .post(`${baseUrl}/addData`, addData, {
            headers: {
              "Content-Type": "application/json",
            },
          })
          .then(function (response) {
            console.log(response);
          })
          .catch(function (error) {
            console.log(error);
          });

Content-Type为 application/x-www-form-urlencoded 时参数需要拼接

    .post(
      "xxxxx",
      // application/x-www-form-urlencoded 的data 需要字符串拼接
      // 如果是"application/json" 可以用对象
      `js_code=${js_code}&appid=x&secret=x&grant_type=x`,
      {
        headers: {
          "Content-Type": "application/x-www-form-urlencoded",
        },
      }
    )
    .then((res) => {
      return res.data;
    })
    .catch((err) => {
      return err;
    });

上传文件：Content-Type为 multipart/form-data

      let file = e.target.files[0];
      let formData = new FormData();

      formData.append("file", file);
      axios
        .post(`${baseUrl}/upload`, formData, {
          headers: {
            "Content-type": "multipart/form-data",
          },
        })
        .then(function (res) {
          console.log(res);
          // innerHTML(response);
        })
        .catch(function (error) {
          console.log(error);
        });

ajax:

$("#ajaxBtn").click(function(){
 $.ajax({
    url:"http://localhost:8080/16_json_ajax_i18n/ajaxServlet",
      headers:{"appId":appId,"appKey":appKey,"Content-Type":"text/plain;charset=UTF,
    data:{action:"jQueryAjax"},
    type:"GET",
    success:function (data) {
    // alert("服务器返回的数据是：" + data);
    // var jsonObj = JSON.parse(data);
     $("#msg").html("编号：" + data.id + " , 姓名：" + data.name);
    },
    dataType : "json"
   });
  });