<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Color Detector</title> <script type="text/javascript"> function calc() { var color = document.getElementById("color").value; if(color.length!=7 && color.length!=9) { alert(color.length + "The format of color is not correct! example: #010203 or #AA010203"); return; } var opacity = 1; if(color.length==9) { opacity = "0x" + color.substring(1, 3); opacity = parseInt(opacity)/255; color = '#' + color.substring(3, color.length); } var boxstyle = document.getElementById('box').style; boxstyle.background=color; boxstyle.opacity =opacity; } </script> </head> <body> <div id="box" style=" 150px; height: 50px; background: #e6e6e6; opacity:1"></div> <input type="text" id="color" name="color" value="#e6e6e6" /> <input type="button" value="Ok" onclick="javascript: calc();"/> </body> </html>