//dialogs.js
function CustomAlert(){

this.render = function(dialog){
    let winW = window.innerWidth;
    let winH = window.innerHeight;
    let dialogoverlay = document.getElementById('dialogoverlay');
    let dialogbox = document.getElementById('dialogbox');
    dialogoverlay.style.display = 'block';
    dialogoverlay.style.height = winH+'px';
    dialogbox.style.left = (winW/2) - (550 * .5)+'px';
    dialogbox.style.top = '100px';
    dialogbox.style.display = 'block';
    document.getElementById('dialogboxhead').innerHTML = 'Acknowledge this message';
    document.getElementById('dialogboxbody').innerHTML = dialog;
    document.getElementById('dialogboxfoot').innerHTML = '<button onclick="Alert.ok()">OK</button>';
};

this.ok = function(){
    document.getElementById('dialogbox').style.display = 'none';
    document.getElementById('dialogoverlay').style.display = 'none';
};

}
export let Alert = new CustomAlert();



  //user.js
  import {Alert} from './dialogs.js';
  .
  .
  .
  .catch(error => {
        console.log('Failure', error);
        Alert.render('Something wrong happened, Please try again.');
    });


    //signup.html
     <script src="js/dialogs.js" type="module"></script>
     <script src="js/user.js" type="module"></script>