JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="a"  value="SUBMIT"  onclick="fnSubmitForm();">

<input type="button" id="b"  value="SUBMIT"  onclick="fnSubmitForm();">

<input type="button" id="c"  value="SUBMIT"  onclick="fnSubmitForm();">

JavaScript

var b = document.querySelectorAll('input[type="button"]');
[].slice.call(b).forEach(function (el) {
  el.onclick = fnSubmitForm.bind(this, el);
});

function fnSubmitForm(el){
  console.log(el.id);
}