效果展示：
inputRange.png
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>range</title>
<style type="text/css">
span{
width:100px;
height: 100px;
border: 1px solid #ccc;
display: block;
}
</style>
</head>
<body>
<input type="range" id="txtR" max="255" min="0" step='1' value="0" oninput="setSpanColor()"></input>
<input type="range" id="txtG" max="255" min="0" step='1' value="0"
oninput="setSpanColor()"></input>
<input type="range" id="txtB" max="255" min="0" step='1' value="0"
oninput="setSpanColor()"></input>
<span id='sp'></span>
<em id="em">(0,0,0)</em>
<script type="text/javascript">
function $$(id){
return document.getElementById(id);
}
function setSpanColor(){
var tR = $$("txtR").value;
var tG = $$("txtG").value;
var tB = $$("txtB").value;
console.log(tR,tG,tB);
var colorRgb = 'rgb('+tR+','+tG+','+tB+')';
$$("em").innerHTML = colorRgb;
$$('sp').style.backgroundColor = colorRgb;
}
setSpanColor()
</script>
</body>
</html>
