web前端第二次作业-编程知识

1，对象

let{

属性

方法

}

2，闭包

只有函数内部的子函数才能读取局部变量，所以闭包可以理解成定义在一个函数内部的函数，在本质上，闭包是将函数内部和函数外部连接起来的桥梁。

3，math

console.log(Math.floor(a))向下取整
console.log(Math.ceil(b)) 向上取整
console.log(Math.max())最大值
console.log(Math.min())最小值
console.log(Math.floor(Math.random() * ((20 - 10) + 1)) + 10)随机数
console.log(Math.round()四舍五入
console.log(Math.sqrt())开平方根
console.log(Math.pow(, ))幂次方

4，date

let year = date.getFullYear()年

let m = date.getMonth() + 1 月

let day = date.getDate()天

let hh = date.getHours()时

let mm = date.getMinutes()分

let ss = date.getSeconds()秒

let w = date.getDay()星期

return `${year}-${m}-${day} ${hh}:${mm}:${ss} 今天星期${w}`}

5，获取元素对象

document.querySelector("css选择器")

document.querySelectorALL 选全部

6，改变元素属性

对象.属性 = 值

7，改变Style样式

1、对象.style.样式 = ""

碰见带-的符合属性，采用小驼峰的方式规避使用

box.classList.add()追加新的类名到元素对象上

box.classList.remove("box1") 移除元素对象的类名

像是checked这样的属性名=属性值的属性，js再进行赋值时，通过true/false去控制属性值

8，事件监听

事件:事件源事件类型处理函数

l0 on事件类型

事件源.on事件类型=function(){}

同一个事件源，后面注册的事件会对前面注册的事件进行覆盖

l1 事件监听不会覆盖

倒计时作业

小米

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