JSFiddle - React, Tailwind, and code Playground

HTML

<button>A</button>
<button>A</button>
<button>A</button>
<button>A</button>
<button>A</button>

JavaScript

function toggleAB(){
  var el = this;
  return [
    function() { el.innerHTML = "A"; },
    function() { el.innerHTML = "B"; }
  ][el.tog^=1]();
}

var btn = document.getElementsByTagName("button");
for(var i=0; i<btn.length; i++) btn[i].onclick = toggleAB;