JavaScript算术运算符包括加法，减法，除法，乘法。让我们来看一些
<html>
<body>
<p id="add"></p>
<script>
var tot = 0;
var a = [1,2,3,4,5,6,7,8,9]
for (var i = 0; i < a.length; i++) {
if(a[i]%2 == 0) {
tot += a[i]
}
}
document.getElementById("add").innerHTML = tot;
</script>
</body>
</html>20
<html>
<body>
<p id="mul"></p>
<script>
var pro = 1;
var a = [1,2,3,4,5,6,7,8,9]
for (var i = 0;i<a.length;i++) {
pro *= a[i]
}
document.getElementById("mul").innerHTML = pro;
</script>
</body>
</html>362880