const rgb = [255, 0, 0];
// Randomly change to showcase updatessetInterval(setContrast, 1000);function setContrast() { // Randomly update colours rgb[0] = Math.round(Math.random() * 255); rgb[1] = Math.round(Math.random() * 255); rgb[2] = Math.round(Math.random() * 255); // http://www.w3.org/TR/AERT#color-contrast const brightness = Math.round(((parseInt(rgb[0]) * 299) +(parseInt(rgb[1]) * 587) +(parseInt(rgb[2]) * 114)) / 1000); const textColour = (brightness > 125) ? 'black' : 'white'; const backgroundColour = 'rgb(' + rgb[0] + ',' + rgb[1] + ',' + rgb[2] + ')'; $('#bg').css('color', textColour); $('#bg').css('background-color', backgroundColour);}#bg { width: 200px; height: 50px;}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><div id="bg">Text Example</div>
