console 命令行工具 X clear

console

function   submit(){
 //获取汉堡包文本框的值
var p=parseInt(document.getElementById("one").value);
//获取薯条文本框的值
var  u=parseInt(document.getElementById("two").value)
//获取可口可乐文本框的值
var col=parseInt(document.getElementById("three").value)
//计算总计：
var  result=Math.ceil(3*p+2*u+1*col)
//把计算的结果放入到总计中
document.getElementById("total").value=result

}
//清空里面的内容
function  clear_value(){

var input=document.getElementsByTagName("input")
var i;
for(i=0;i<input.length;i++){
    input[i].value=""
}
}

<!doctype  html>
<html>
<head>
	<title>麦丹劳点餐系统</title>
</head>

<body>
	<span>&nbsp;&nbsp;汉堡包：&yen3</span>
    <input type="number"  id="one"><br/>
    <span>&nbsp;&nbsp;&nbsp;&nbsp;薯条：&yen2</span>
    <input type="number"  id="two""><br/>
    <span>可口可乐：&yen1</span>
    <input type="number"  id="three"><br/>
    <button   onclick="submit()">提交</button>&nbsp;&nbsp;
    <button    onclick="clear_value()">清空</button>
    <br/>
    <br/>
    <span>总计</span>
    <input type="number" id="total">
</body>

</html>