Javascript callback function not able to access parent function variables

Question

I am very new to Javascript i am trying to understand callback for my project work to get text box input as address and want to do my core work on button click. In html side i am having N text boxes, for each address from text boxes same function has to work

window.addEventListener('load', function(){

var variable1;
var variable2;

Buttons = document.getElementsByClassName('Do');
  for (var i = 0; i < Buttons .length; i++) {
    Buttons [i].addEventListener('click',Do);
  }

  function Do(event){
    let Id = event.target.parentNode.parentNode.id;
    let Tag = document.getElementById(Id);
    let address = Tag.children[1];
    callbackfn.bind(this);
    backendlibraryfuntion(callbackfn);
  }
  function callbackfn(x,y){
    console.log(variable1); //working perfectly
    console.log(variable2); //working perfectly
    console.log(address); // throwing undefined error 
  }
  
});

I am facing issue while accessing address value in callback , my objective is to get N address and initiate N Parallel instances based on address. can some one help me for this.

Answer 1

Define address variable near variable1 and variable2 then you will not face this particular error.

var variable1;
var variable2;
let address;