[04--JS] 布尔值boolean
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
// ""(空字符串)、0、null、undefined、NaN都是false。
console.log(Boolean("")); // false
console.log(Boolean(null)); // false
console.log(Boolean(undefined)); // false
console.log(Boolean(NaN)); // false
</script>
</head>
<body>
</body>
</html>