使用promise -纯javascript发送带参数(数据)的post请求

function postData(url, data) {
  return new Promise(function(resolve, reject) {
    var xhr = new XMLHttpRequest();
    xhr.open("POST", url, true);
    xhr.setRequestHeader("Content-Type", "application/json");
    xhr.onreadystatechange = function() {
      if (xhr.readyState === 4) {
        if (xhr.status === 200) {
          resolve(xhr.responseText);
        } else {
          reject(xhr.statusText);
        }
      }
    };
    xhr.onerror = function() {
      reject(xhr.statusText);
    };
    xhr.send(JSON.stringify(data));
  });
}

var url = "https://example.com/api";
var data = { name: "John", age: 30 };

postData(url, data)
  .then(function(response) {
    console.log("POST request succeeded:", response);
  })
  .catch(function(error) {
    console.error("POST request failed:", error);
  });