WebStorage(js本地存储)

存储内容大小一般支持5MB左右(不同浏览器可能还不一样)
浏览器端通过Window.sessionStorage 和Winodw.localStorage 属性来实现本地存储机制相关API
xxxStorage.setItem(‘key’,‘value’)该方法接受一个键和值作为参数，会把键值对添加到存储中，如果键名存在，则更新其对应的值
xxxStorage.getItem(‘key’)该方法接受一个键名作为参数，返回键名对应的值。
xxxStorage.removeItem(‘key’)该方法接受一个键名作为参数，并把该键名从存储中删除
xxxStorage.clear()该方法会清空存储中的所有数据。
备注

SessionStorage 存储的内容会随着浏览器窗口关闭而消失
LocalStorage 存储的内容，需要手动清除才会消失
xxxStorage.getItem(xxx) 如果xxx对应的value获取不到，那么getItem()的返回值是null
JSON.parse(null)的结果依然是null

localStorage

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8" />
		<title>localStorage</title>
	</head>
	<body>
		<h2>localStorage</h2>
		<button onclick="saveData()">点我保存一个数据</button>
		<button onclick="readData()">点我读取一个数据</button>
		<button onclick="deleteData()">点我删除一个数据</button>
		<button onclick="deleteAllData()">点我清空一个数据</button>

		<script type="text/javascript" >
			let p = {name:'张三',age:18}

			function saveData(){
				localStorage.setItem('msg','hello!!!')
				localStorage.setItem('msg2',666)
				localStorage.setItem('person',JSON.stringify(p))
			}
			function readData(){
				console.log(localStorage.getItem('msg'))
				console.log(localStorage.getItem('msg2'))

				const result = localStorage.getItem('person')
				console.log(JSON.parse(result))

				// console.log(localStorage.getItem('msg3'))
			}
			function deleteData(){
				localStorage.removeItem('msg2')
			}
			function deleteAllData(){
				localStorage.clear()
			}
		</script>
	</body>
</html>

sessionStorage

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8" />
		<title>sessionStorage</title>
	</head>
	<body>
		<h2>sessionStorage</h2>
		<button onclick="saveData()">点我保存一个数据</button>
		<button onclick="readData()">点我读取一个数据</button>
		<button onclick="deleteData()">点我删除一个数据</button>
		<button onclick="deleteAllData()">点我清空一个数据</button>

		<script type="text/javascript" >
			let p = {name:'张三',age:18}

			function saveData(){
				sessionStorage.setItem('msg','hello!!!')
				sessionStorage.setItem('msg2',666)
				sessionStorage.setItem('person',JSON.stringify(p))
			}
			function readData(){
				console.log(sessionStorage.getItem('msg'))
				console.log(sessionStorage.getItem('msg2'))

				const result = sessionStorage.getItem('person')
				console.log(JSON.parse(result))

				// console.log(sessionStorage.getItem('msg3'))
			}
			function deleteData(){
				sessionStorage.removeItem('msg2')
			}
			function deleteAllData(){
				sessionStorage.clear()
			}
		</script>
	</body>
</html>