SOURCE

// 实现Storage，使得该对象为单例，基于 localStorage 进行封装。实现方法 setItem(key,value) 和 getItem(key)

/*
*	静态方法
*/
class Storage {
	staic getInstance () {
		if (!Storage.instance) {
			Storage.instance = new Storage()
		}
		return Storage.instance
	}
	getItem (key) {
		return localStorage.getItem(key)
	}
	setItem (key, value) {
		return localStorage.setItem(key, value)
	}
}
/*
*	闭包版
*/
function StorageBase () {}
StorageBase.prototype.getItem = function (key) {
	return localStorage.getItem(key)
}
StorageBase.prototype.setItem = function (key, value) {
	return localStorage.setItem(key, value)
}

const Storage = (function () {
	let instance = null
	return function () {
		if (!instance) {
			instance = new StorageBase()
		}
		return instance
	}
})()