<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>函数function</title>
<!--
function 函数名(参数1,参数2,.....参数n){
执行语句1;
执行语句2;
...
执行语句n;
}
调用函数的方法：
函数名(参数1,参数2;...);
-->
</head>
<body>
<script>
function sum(a,b,c,d){
var y=a+b+c+d;
document.write(y+"<br />");
var x=a-b;
document.write(x+"<br />");
}
sum(1,2,3,4);//页面中会有两个值
sum(1,3)//页面中会有两个值
</script>
</body>
</html>
