为什么结果会出现16 undefined12 undefined的情况，求解答！
慕工程8359979
2017-03-27 00:02
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>函数传参</title>
<script type="text/JavaScript">
function add3(x,y,z)
{
sum = x+y+z;
document.write(sum+"<br/>");
}
document.write(add3(5,8,3));
document.write(add3(7,1,4));
</script>
</head>
<body>
</body>
</html>
3回答
-
- Robert_Langdon
- 2017-04-04 17:54:08
add3(5,8,3)运算完是16，电脑输出16，你又在外面包了个document.write，此时document.write(add3(5,8,3))那就是document.write(16)，这什么也不是，只能输出undefined了
-
- 慕工程8359979
- 2017-03-28 19:25:44
document.write(document.write(16));
add3(5,8,3)
这部分是什么意思呢?
-
- 水滴石狮
- 2017-03-27 00:51:12
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>函数传参</title>
<script type="text/JavaScript">
function add3(x,y,z)
{
sum = x+y+z;
document.write(sum+"<br/>");
}
document.write(document.write(16));
add3(5,8,3)
document.write(document.write(12));
add3(7,1,4)
</script>
</head>
<body>
</body>
</html>
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