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In absolute positioning, what parameters can be used as a reference?

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Absolute positioning is a layout method commonly used in front-end development. It can accurately place elements at specified positions and follow the page scroll without position changes. When performing absolute positioning, we need to refer to some parameters to ensure that the element can be accurately positioned at the desired location. This article will introduce several commonly used parameters as a reference and give specific code examples.

1. Left, top, right, and bottom parameters

In absolute positioning, specify the left side of the element relative to its containing element by setting the left, top, right, and bottom parameters of the element. , upper, right and lower offsets. These parameters can be specific pixel values or percentage values.

Code example:

<!DOCTYPE html>
<html>
  <head>
    <style>
      .container {
        position: relative;
        width: 400px;
        height: 400px;
        background-color: lightgray;
      }
      .box {
        position: absolute;
        left: 50px;
        top: 50px;
        width: 200px;
        height: 200px;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="box"></div>
    </div>
  </body>
</html>

In the above code, the box element is positioned 50px offset from the upper left corner of the container element by setting the left and top parameters to 50px.

2. Z-index parameter

There may be multiple elements on the page for absolute positioning. If these elements overlap, the z-index parameter can be used to control the stacking order of the elements. Elements with larger z-index values are placed closer to the front and will cover other elements.

Code example:

<!DOCTYPE html>
<html>
  <head>
    <style>
      .container {
        position: relative;
        width: 400px;
        height: 400px;
        background-color: lightgray;
      }
      .box1 {
        position: absolute;
        left: 50px;
        top: 50px;
        width: 200px;
        height: 200px;
        background-color: red;
        z-index: 1;
      }
      .box2 {
        position: absolute;
        left: 100px;
        top: 100px;
        width: 200px;
        height: 200px;
        background-color: blue;
        z-index: 2;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="box1"></div>
      <div class="box2"></div>
    </div>
  </body>
</html>

In the above code, the z-index value of the box1 element is 1, and the z-index value of the box2 element is 2, so the box2 element will cover the box1 element above.

3. Position the position attribute of the parent element

When performing absolute positioning, you need to pay attention to the position attribute of the parent element. If the position attribute is not set on the positioned parent element, the position of the absolutely positioned element will be positioned relative to the visible area of the document. If the positioned parent element has the position attribute set, the position of the absolutely positioned element will be positioned relative to the positioned parent element.

Code example:

<!DOCTYPE html>
<html>
  <head>
    <style>
      .container {
        position: relative;
        width: 400px;
        height: 400px;
        background-color: lightgray;
      }
      .box1 {
        position: absolute;
        left: 50px;
        top: 50px;
        width: 200px;
        height: 200px;
        background-color: red;
      }
      .box2 {
        position: absolute;
        left: 100px;
        top: 100px;
        width: 200px;
        height: 200px;
        background-color: blue;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="box1"></div>
      <div class="box2"></div>
    </div>
  </body>
</html>

In the above code, the positioning parent element of the box1 and box2 elements is the container element, so the box1 and box2 elements are positioned relative to the container element.

Absolute positioning is a very common layout method in front-end development. By referring to the above parameters, elements can be positioned flexibly and accurately. In actual development, we can flexibly use these parameters according to needs to achieve diverse page layouts.

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