Electron js - Calling a function from another

To call a function from another, we have to use this references. For e.g.

var oReq = new XMLHttpRequest();
    oReq.onload = this.reqListener;
    oReq.onerror = this.reqError;
    oReq.open('get', './api/some.json', true);
    oReq.send();


reqListener() {
    console.log('reqListener called');
    var data = JSON.parse(this.responseText);
    console.log(data);
  }
 
  reqError(err) {
    console.log('reqError called');
    console.log('Fetch Error :-S', err);
  }

If this is omitted from the onload assignment, then it complaints that the method not found.


References