1 <!DOCTYPE html> 2 <html> 3 <head> 4 <meta charset="UTF-8"> 5 <title>Document</title> 6 </head> 7 <style> 8 #demo{ 9 600px; 10 height: 600px; 11 } 12 </style> 13 <body> 14 <div id="demo"></div> 15 <script> 16 var div = document.getElementById("demo"); 17 randomColor(div); 18 function randomColor(div) { 19 r = Math.ceil(Math.random()*255); 20 g = Math.ceil(Math.random()*255); 21 b = Math.ceil(Math.random()*255); 22 a = (Math.random()).toFixed(1); 23 div.style.background = "rgb(" + r + "," + g + "," + b + "," + a + ")"; 24 } 25 </script> 26 </body> 27 </html>