<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<div class="box"></div>
<div class="box" id="box2"></div>
<script src="http://static01.baomihua.com/js/lib/jquery-1.4.4.min.js"></script>
<script>
'use strict' // 5种原始类型：字符串、数字、布尔值、null和undefined
console.log(typeof '' === 'string') // 字符串
console.log(typeof 5 === 'number') // 数字
console.log(typeof true === 'boolean') // 布尔值
console.log(typeof a === 'undefined') // undefined var element = document.getElementById('box1')
var element2 = document.getElementById('box2')
console.log(element === null) // null console.log(document.getElementById('box2').className === 'box')
console.log($('#box2')[0].className === 'box')
console.log($('.box')[$('.box').length - 1].className === 'box')
console.log($('#box3').length === 0)
console.log(typeof $('#box3')[0] === 'undefined')
console.log(typeof [][0] === 'undefined') // 引用值：Object、Array、Date、Error
console.log(typeof null === 'object')
var now = new Date()
console.log(now instanceof Date) // Date
console.log(/a/ instanceof RegExp) // RegExp function Person(name) {
this.name = name
}
var me = new Person('Nicholas')
console.log(me instanceof Person)
console.log(typeof Person === 'function') // function
function isArray(value) {
if (typeof Array.isArray === 'function') {
return Array.isArray(value)
} else {
return Object.prototype.toString.call(value) === '[object Array]'
}
}
console.log(isArray([])) // array var object = {
count: 0,
related: null
}
if ('count' in object) { // 属性
console.log('ca')
}
if (me.hasOwnProperty('name')) { // 实例属性
console.log('ca')
}
if ('hasOwnProperty' in element2 && element2.hasOwnProperty('name')) { // IE8以及更早版本的IE中，DOM对象并非继承自Object，因此也不包含这个方法
console.log('ca')
}
</script>
</body>
</html>