面试题三（上）

1. 盒子居中的实现方法

对于不定宽的div居中:
1. margin：0 auto
2. 盒模型（给父元素设置）
display: flex;
justify-content: center;
align-items: center;
3.
position: absolute;
left: 50%;
transform: translateX(-50%);
4.margin: auto;
position: absolute;
left: 0;
right: 0;
对于定宽的div居中:
1. position:absolute;
left:50%;
margin-left:宽/2

对于不定宽的div居中:
1. margin：0 auto
2. 盒模型（给父元素设置）
display: flex;
justify-content: center;
align-items: center;
3.
position: absolute;
left: 50%;
transform: translateX(-50%);
4.margin: auto;
position: absolute;
left: 0;
right: 0;
对于定宽的div居中:
position:absolute;
left:50%;
margin-left:宽/2

---

2.function Person(){

}
Person.prototype.showFavour=function(){
    console.log("111");
}
function Teacher(){

}
Teacher.prototype=Person.prototype;
Teacher.prototype.showFavour=function(){
    console.log("222");
}
var pers=new Person();
pers.showFavour();
var tea=new Teacher();
tea.showFavour();
两个输出的结果是？？？
答：console.log("222");

今天不想说话......