JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="hex" placeholder="hex">
<input type="text" id="rgb" placeholder="rgb">

JavaScript

$('#hex').bind('blur keydown', function (event) {
  setTimeout(function () {
    var rgb = [],
        broken = false,
        value = $("#hex").val(),
        hex = (value+'').replace(/#/, '');

    if (value.length === 1 && value !== '#') {
      $("#hex").val(value);
    }

    if (hex.length == 3) hex = hex + hex;
    for (var i = 0; i < 6; i+=2) {
      rgb.push(parseInt(hex.substr(i,2),16));
      broken = broken || rgb[rgb.length - 1].toString() === 'NaN';
    }

    $('#rgb').val(broken ? '' : 'rgb(' + rgb.join(',') + ')');   
  }, 13);
});