面向对象

三要素

封装

继承

多态

意义

数据结构化
👇
抽象 --> 简单

应用

jQuery中的应用

class jQuery {
	constructor(selector) {
		const slice = Array.prototype.slice
		const $el = slice.call(document.querySelectorAll(selector))
		const len = $el.length
		for (let i = 0; i < len; i++) {
			this[i] = $el[i]
		}
		this.selector = selector
		this.length = len
	}
	addClass() {}
}

window.$ = function (selector) {
	return new jQuery(selector)
}

const $h = $('h2')
console.log($h)
const $p = $('section')
console.log($p)