98 lines
2.3 KiB
Markdown
98 lines
2.3 KiB
Markdown
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---
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title: Z Index
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---
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## Z Index
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Z Index (`z-index`) is a CSS property that defines the order of overlapping HTML elements. Elements with a higher index will be placed on top of elements with a lower index.
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**Note**: Z index only works on positioned elements (`position:absolute`, `position:relative`, or `position:fixed`).
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#### Possible Values
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```css
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/* Default value if not specified */
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z-index: auto;
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/* Integer values */
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z-index: 1;
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z-index: 100;
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z-index: 9999;
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z-index: -1;
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/* Global values */
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z-index: inherit;
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z-index: initial;
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z-index: unset;
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```
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#### Example Usage
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In this example, you can see three boxes displayed on top of each other in different orders using `z-index`.
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<em>HTML</em>
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```html
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<div class="container">
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<div class="box" id="blue"></div>
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<div class="box" id="red"></div>
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<div class="box" id="green"></div>
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</div>
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```
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<em>CSS</em>
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```css
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#blue {
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background-color: blue;
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}
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#red {
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background-color: red;
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}
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#green {
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background-color: green;
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}
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```
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Since `z-index` wasn't defined, it will have a default value of `auto`. This is a result:
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Try to change the order to Green, Blue, Red in CSS using `z-index`.
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```css
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#blue {
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background-color: blue;
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z-index: 2;
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}
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#red {
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background-color: red;
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z-index: 1;
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}
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#green {
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background-color: green;
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z-index: 3;
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}
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```
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Your result will be:
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Use Z Index if you need to put a background element below a container. You can easily place the background under every element by giving it a negative Z Index like below:
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```css
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#background {
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z-index: -1;
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}
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```
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#### More Information:
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<!-- Please add any articles you think might be helpful to read before writing the article -->
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<a href="https://css-tricks.com/almanac/properties/z/z-index/" target="_blank">https://css-tricks.com/almanac/properties/z/z-index/</a>
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<a href="https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index" target="_blank">https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Positioning/Understanding_z_index</a>
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<a href="https://philipwalton.com/articles/what-no-one-told-you-about-z-index/" target="_blank">https://philipwalton.com/articles/what-no-one-told-you-about-z-index/</a>
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