css实现8种居中布局

<div class='box' >
　　<div class='center' ></div>
</div>

 

        // 样式
        .box {
            width: 700px;
            height: 700px;
            border: 1px solid red;
        }
        .center {
            width: 100px;
            height: 100px;
            border: 1px solid green;
        }

        // 第一种
        .box {
            display: grid;
        }
        .center {
            align-self: center;
            justify-self: center;
        }

        // 第二种            
        .box {
            display: grid;
            place-items: center;
        }
        .center {}

        // 第三种
        .box {
            display: table-cell;
            vertical-align: middle;
        }

        .center {
            margin: auto;
        }

        // 第四种
        .box {
            display: flex;
            justify-content: center;
            align-items: center;
        }
        .center {}

        // 第五种
        .box {
            position: relative;
        }
        .center {
            position: absolute;
            left: 0;
            right: 0;
            top: 0;
            bottom: 0;
            margin: auto;
        }

        // 第六种
        .box {
            position: relative;
        }
        .center {
            position: absolute;
            left: calc(50% - 50px);
            top: calc(50% - 50px);
        }

        // 第七种
        .box {
            position: relative;
        }
        .center {
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }


        // 第八种
        .box {
            position: relative;
        }
        .center {
            position: absolute;
            left: 50%;
            top: 50%;
            margin-left: -50px;
            margin-top: -50px;
        }