null和undefined相等比较
在==(相等)判断中,null和undefined相等(它们也与自身相等),除此之外不与其他值相等。
示例代码:
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8" />
<title>null和undefined相等比较</title>
</head>
<body>
<script type="text/javascript">
var a = null;
var b;
console.log(a == b); //true
console.log(a == null); //true
console.log(b == null); //true
console.log(a == false); //false
console.log(b == false); //false
console.log(a == ''); //false
console.log(b == ''); //false
console.log(a == 0); //false
console.log(b == 0); //false
</script>
</body>
</html>
判断对象是null,Object,Date
const isObject = Object.prototype.toString.call(value).toLowerCase() === '[object object]';
const isNull = Object.prototype.toString.call(value).toLowerCase() === '[object null]';
Object.prototype.toString.call(dateObj) !== '[object Date]'
作者:孟繁贵 Email:meng010387@126.com 期待共同进步!