JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" class="null">
<input type="text" class="undefined">
<input type="text" class="nil">

JavaScript

const nullInput = document.querySelector('input.null');
const undefinedInput = document.querySelector('input.undefined');
const nilInput = document.querySelector('input.nil');

let a = null;
let b;
let c = 0;

nullInput.value = a;
undefinedInput.value = b;
nilInput.value = c;