JSFiddle - React, Tailwind, and code Playground

by María Fernández

HTML

<button type="button">counter/altFunc</button>

<p></p>

JavaScript

var a = 0;
function add() {
  return a += 1;
}
function execute_counter() {
  document.getElementsByTagName('P')[0].innerHTML = add();
}

var b = setInterval(execute_counter, 1000);

function counter() {
  document.getElementsByTagName('BUTTON')[0].removeEventListener('click', counter);
  document.getElementsByTagName('BUTTON')[0].addEventListener('click', altFunc);
  setInterval(execute_counter, 1000);
}

function altFunc() {
  document.getElementsByTagName('BUTTON')[0].removeEventListener('click', altFunc);
  document.getElementsByTagName('BUTTON')[0].addEventListener('click', counter);
  clearInterval(b);
}

document.getElementsByTagName('BUTTON')[0].addEventListener('click', altFunc);