JSFiddle - React, Tailwind, and code Playground

HTML

<h2 id="contoh">
A 000
</h2>

<button id='lanjut'>
Lanjut
</button>

JavaScript

let a = document.getElementById('contoh');
let b = document.getElementById('lanjut');

var angka = 0;
b.onclick = function(e){
let d = a.innerHTML.slice(3,-1);
let c = onClick3();

  if(c < 10){
  	a.innerHTML = 'A 00'+c;
  }
  if(c > 10 && c < 100){
  	a.innerHTML = 'A 0'+c;
  }
  if(c > 100 && c < 1000){
  	a.innerHTML = 'A '+c;
  }
}

function onClick3() {
  return angka += 1;
};