Summary of multiple horizontal and vertical centering methods

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1. The elements in the row are centered horizontally

Method 1.text-align:center;

Code demo

    <style>
        .parent {
            background-color: red;
            text-align: center;
            height: 40px;
        }
    </style>
</head>

<body>
    <!-- 行内元素居中  水平居中 给父元素设置也可以因为有继承性 -->
    <div class="parent">
        <span class="child">行内元素水平居中</span>
    </div>
</body>

Method 2.width:fit-content;

Code demo

     <style>
        .box {
            background-color: red;
        }
        
        .parent {
            background-color: pink;
            /* 此时父元素的宽度会适应子元素的宽度 然后在父元素身上加上margin 即可水平居中 */
            width: fit-content;
            margin: auto;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="parent">
            <span class="child">行内元素水平居中</span>
        </div>
    </div>
</body>

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2. In-line elements are vertically centered

Method 1.line-height (only for single-line text, multi-line text does not take effect)

    <style>
        .box {
            width: 200px;
            line-height: 200px;
            background-color: red;
        }
    </style>
</head>

<body>
    <div class="box">
        <span class="child">垂直居中</span>
    </div>
</body>

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3. Block-level elements are centered horizontally

Method 1.margin: 0 auto;

Code demo

    <style>
        .parent {
            background-color: red;
        }
        
        .child {
            width: 150px;
            margin: 0 auto;
            background-color: pink;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child">块级元素水平居中</div>
    </div>
</body>

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Four. Achieve horizontal and vertical centering

Method 1. Positioning to achieve

Code demo

    <style>
        .parent {
            position: relative;
            height: 200px;
            background-color: red;
        }
        
        .child {
            position: absolute;
            top: 50%;
            left: 50%;
            /* 减去子元素高宽自身的一半 */
            margin-top: -50px;
            margin-left: -50px;
            height: 100px;
            width: 100px;
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child"></div>
    </div>
</body>

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Method 2. Positioning + transform

Code demo

    <style>
        .parent {
            position: relative;
            height: 200px;
            background-color: red;
        }
        
        .child {
            position: absolute;
            width: 100px;
            height: 100px;
            top: 50%;
            left: 50%;
            /* 用transform 可以动态检测到子元素的宽高了 如果子元素宽高改变了我们不用担心了 */
            transform: translate(-50%, -50%);
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child"></div>
    </div>
</body>

Insert picture description here
Method 3. Positioning + margin

Code demo

   <style>
        .parent {
            position: relative;
            height: 200px;
            background-color: red;
        }
        
        .child {
            width: 100px;
            height: 100px;
            /* 原理就是让top left right bottom 设置为0 此时子元素会填充父元素所有可用空间 就有了可分配空间 然后在设置margin水平方向居中即可 */
            position: absolute;
            top: 0px;
            left: 0px;
            bottom: 0px;
            right: 0px;
            margin: auto;
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child"></div>
    </div>
</body>

Insert picture description here
Method 4.padding to achieve

Code demo

    <style>
        .parent {
            /* 父元素没有设置宽高  子元素的宽高就是父元素的宽高*/
            background-color: red;
            padding: 20px;
        }
        
        .child {
            height: 100px;
            background-color: blue;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child"></div>
    </div>
</body>

Insert picture description here
Method 5.flex to achieve

Code demo

    <style>
        .parent {
            height: 200px;
            display: flex;
            /* 垂直居中 */
            align-items: center;
            /* 水平居中 */
            justify-content: center;
            background-color: red;
        }
        
        .child {
            width: 100px;
            height: 100px;
            background-color: pink;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="child"></div>
    </div>
</body>

Insert picture description here