Post-on-load

post-on-page-load.js

window.onload = function () {
  postJsonData().then(function (theResult) {
      console.log("theResult: " + theResult);
      // do something else if necessary
  });
}

function getJsonData() {
  targetUrl = "https://api.etcetc.com/gooo";
  return new Promise(function (resolve, reject) {
      var request = new XMLHttpRequest();
      request.open("GET", targetUrl, true);
      request.setRequestHeader("content-type", "application/json");
      request.send(null);
      request.onreadystatechange = function() {
          if (request.readyState === 4) {
              if (request.status === 200) {
                  var respJson = JSON.parse(request.responseText);
                  resolve(respJson);
              }
          }
      } // onreadystatechange
  });
} // var myJsonData

function postJsonData() {
  targetUrl = "https://api.etcetc.com/gooo";
  var xhr = new XMLHttpRequest();
  xhr.open("POST", targetUrl, true);
  xhr.setRequestHeader("Content-type", "application/json");
  xhr.onreadystatechange = function () {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var json = JSON.parse(xhr.responseText);
        console.log(json.email + ", " + json.password);
    }
  };
  // body data to post
  var data = JSON.stringify({"key1": "val1", "key2": "val2"});
  xhr.send(data);
}