容器内元素水平垂直居中

<div id="wrap">

　　<div id="box">

　　</div>
</div>

效果图

方法一

　　　　#wrap{
            width: 300px;
            height: 300px;
            background: lightblue;
            position: relative;
        }
        #box{
            width: 150px;
            height: 150px;
            background: pink;
            position: absolute;
            top:50%;
            left:50%;
            transform: translate(-50%,-50%);
        }

方法二

        #wrap{
            width: 300px;
            height: 300px;
            background: lightblue;
            position: relative;
        }
        #box{
            width: 150px;
            height: 150px;
            background: pink;
            position: absolute;
            top:0;
            left:0;
            right:0;
            bottom:0;
            margin:auto;
        }    

 方法三

        #wrap{
            width: 300px;
            height: 300px;
            background: lightblue;
            position: relative;
        }
        #box{
            width: 150px;
            height: 150px;
            background: pink;
            position: absolute;
            top:50%;
            left:50%;
            margin-left: -75px;
            margin-top: -75px;
        }

方法四

        #wrap{
            width: 300px;
            height: 300px;
            background: lightblue;
            display: flex;
            justify-content:center;
            align-items:center;
        }
        #box{
            width: 150px;
            height: 150px;
            background: pink;
        }