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AJAX介绍

news 2025/8/7 8:44:51

XMLHttpRequest

get请求使用

const xhr = new XMLHttpRequest();
xhr.open("GET", "/data/test.json", true);
xhr.onreadystatechange = function () {
  if (xhr.readyState === 4) {
    if (xhr.status === 200) {
      alert(xhr.responseText);
    } else {
      console.log("其他情况");
    }
  }
};

xhr.send(null);

post请求

const xhr = new XMLHttpRequest();
xhr.open("POST", "/data/test.json", true);
xhr.onreadystatechange = function () {
  if (xhr.readyState === 4) {
    if (xhr.status === 200) {
      alert(xhr.responseText);
    } else {
      console.log("其他情况");
    }
  }
};

const postData = {
  userName: "zhangsan",
  password: "xxx",
};

xhr.send(JSON.stringify(postData));

xhr.readyState

用的最多的还是4

xhr.status

手写AJAX

function myAjax(url, method = "GET", data = null, headers = {}) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.open(method, url, true);
    for (const [key, value] of Object.entries(headers)) {
      xhr.setRequestHeader(key, value);
    }

    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4) {
        if (xhr.status >= 200 && xhr.status < 300) {
          try {
            const response = xhr.responseText
              ? JSON.parse(xhr.responseText)
              : null;
            resolve(response);
          } catch (error) {
            reject(new Error("JSON解析失败"));
          }
        } else {
          const errorMap = {
            400: "请求参数错误",
            401: "未授权",
            403: "禁止访问",
            404: "资源未找到",
            500: "服务器内部错误",
          };
          reject(
            new Error(errorMap[xhr.status] || `请求失败，状态码：${xhr.status}`)
          );
        }
      }
    };
    xhr.send(method.toUpperCase() === "GET" ? null : data);
  });
}