CSS | Центрирующие элементы

Иногда мы сталкиваемся с проблемами центрирования элемента на веб-странице. Неужели это так сложно? Центрировать элемент не так уж и сложно. Есть так много разных способов сделать это.
Единственное, что нам нужно знать, это то, какая техника для какой цели. Как только вы поймете проблему, подобрать лучшую технику станет намного проще.

So let us see some situation and discuss the best method to achieve the goal.

1. Horizontally
   • Inline elements
     We can easily center an inline element within a block level element like this:

     // Aligning text in center .center {      text-align: center; }

   • Block level elements
     We can center a block-level element by giving it margin-left and margin-right of auto (which has a known specified width):

     // Aligning an element of defined length in center // Remember to define the width of the element otherwise it  //will be full width and "auto" will not work .center  {     margin: 0 auto;     width: 200px; }

   • More than one block level elements
     If we have two or more block-level elements that need to be centered horizontally in a row, it can be better served making them a different display type display: inline-block;

     .parent {   // Aligning the child of this parent in center   text-align: center; } .child {   // set the display of child elements    display: inline-block;   text-align: left; }

2. Vertically
   • Inline elements
     We can easily center an inline element within a block level element like this:

     // Set the display of the parent class as table .parent {   display: table;   height: 250px;   background: white;   width: 240px;   margin: 20px; }   // Set the display of the child class as table-cell .child {   display: table-cell;   margin: 0;   background: black;   color: white;   padding: 20px;   border: 10px solid white;   vertical-align: middle; }

   • Block level elements of known height
     We can easily center an inline element within a block level element like this:

     // Set the position of the parent as relaive to other           .parent  {   position: relative; }   // Set position of the child as absolute in its parent class // so that it can be placed anywhere in the parent class .child  {   position: absolute;   top: 50%;   height: 100px;     /* responsible for padding and border    if not using box-sizing: border-box; */   margin-top: -50px;  }

     Block level elements of unknown height
     We can easily center an inline element within a block level element like this:

     // Set position of child as absolute in its parent class            .parent  {   position: relative; }   // Set top of the child 50% of viewport // Translat the child by 50% of its height about       // negative y axis .child  {   position: absolute;   top: 50%;   transform: translateY(-50%); }

3. Both Horizontally & Vertically
   • Element with fixed height and width
     Using negative margins equal to half of that width and height, after you’ve absolutely positioned it at 50% / 50% will center it.

     // Set position of parent class as relative .parent  {   position: relative; }   // Set top and left of an element of // known height as 50% .child  {   width: 300px;   height: 100px;   padding: 20px;     position: absolute;   top: 50%;   left: 50%;     margin: -70px 0 0 -170px; }

   • Element with unknown height and width
     When we don’t know the width or height, we can use the transform property and a negative translate of 50% in both directions to center:

     // Set position of parent as relative to other .parent  {   position: relative; }   // Set top and left of an element of  // known height as 50%. Translate the // element 50% of its height and width   // about negative x-axis and negative y-axis .child  {   position: absolute;   top: 50%; //    left: 50%;   transform: translate(-50%, -50%); }

Note: The ‘.’ operator is used in CSS to identify a CSS class. In the above examples, the class parent is used to style the parent element and the class child is used for the child element.