javascript笔记02:严格模式的特定要求

1.严格模式变量必须声明,不然会报错:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title>严格模式</title>

</head>



<body>

<script type="text/javascript">

"use strict";

try {

    i = 1;

}catch(err) {

    alert(err);

}

</script>

</body>

</html>

这里i没有使用var修饰,就是没有定义的意思,后抛出"undeclared variable i"错误

 

2.严格模式下,不能删除全局变量函数函数的参数

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title>严格模式</title>

</head>



<body>

<script type="text/javascript">

"use strict";

var i;

function myfunc() {};

delete i;//语法错误

delete myfunc();//语法错误
function myfunc2(arg) 
{
delete arg;//语法错误

}
</script> 
</body>
</html>

 

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