ajax post this page

function postData(url) {
    return new Promise((resolve, reject) => {
      var xhr = new XMLHttpRequest();
      xhr.open("POST", url);
      xhr.onload = function() {
        var data = xhr.responseText;
        resolve(data);
      };
      xhr.onerror = function() {
        reject(Error(xhr.statusText));
      };
      xhr.send();
    });
  }
  
  postData("/data.json")
    .then(data => {
      console.log(data);
    })
    .catch(error => {
      console.error(error);
    });