JSFiddle - React, Tailwind, and code Playground

by Farzad Cyrus

HTML

<div id="content">
<span>#223355</span>
</div>

CSS

html, body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}
div {
  width: 100%;
  height: 100%;
  position: absolute;
  left: 0;
  right: 0;
  background: #223355;
  text-align: center;
  color: #fff;
}
span {
  position: absolute;
  top: 50%;
  left: 50%;
  margin: -100px 0 0 -300px;
  width: 600px;
  height: 200px;
  display: block;
  color: #fff;
  font-size: 72px;
  line-height: 200px;
}

JavaScript

function lightenDarkenColour(col,amt) {
    var usePound = false;
    if ( col[0] == "#" ) {
        col = col.slice(1);
        usePound = true;
    }

    var num = parseInt(col,16);

    var r = (num >> 16) + amt;

    if ( r > 255 ) r = 255;
    else if  (r < 0) r = 0;

    var b = ((num >> 8) & 0x00FF) + amt;

    if ( b > 255 ) b = 255;
    else if  (b < 0) b = 0;

    var g = (num & 0x0000FF) + amt;

    if ( g > 255 ) g = 255;
    else if  ( g < 0 ) g = 0;

    return (usePound?"#":"") + (g | (b << 8) | (r << 16)).toString(16);
}



var content = document.querySelector('#content');

content.style.background = lightenDarkenColour('#dd2244', 128);