Quick method to Ajax with pure JS

fetch.js

let fetch = (url, body) => {
  return new Promise( async function (resolve, reject) {
    // IF MODERN BROWSER > CREATE NEW httpRequest
    let httpRequest;
    if (window.XMLHttpRequest) {
      httpRequest = new XMLHttpRequest();
    }
    // IF IE > CREATE NEW ActiveXObject
    else if (window.ActiveXObject) {
      try {
        httpRequest = new window.ActiveXObject("Msxml2.XMLHTTP");
      } catch (e) {
        try {
          httpRequest = new window.ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
      }
    }

    // UNABLE TO CREATE httpRequest
    if (!httpRequest) {
      resolve( false );
    }

    //add a listener for the "load" event, which
    //will happen when the data returns
    httpRequest.addEventListener("load", function() {
      if (httpRequest.status >= 200 && httpRequest.status < 400) {
        const txt = httpRequest.responseText; // Success!
        resolve( txt[0] === "{" || txt[0] === "[" ? JSON.parse(txt) : txt );
      } else {
        // We reached our target server, but it returned an error
        reject(httpRequest.status)
      }
    });

    //add a listener for the "error" event, which
    //will happen if there was a network error
    httpRequest.addEventListener("error", function(e) {
      reject(e)
    })

    // SEND REQUEST
    httpRequest.open(body?'POST':'GET', url);
    httpRequest.send(body?JSON.stringify(body):undefined);
  })
};