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How to set height in css
- PHPzOriginal
- 2023-04-06 12:44:123792browse
CSS is a very important front-end technology. We often use CSS to adjust the style of web pages, such as fonts, colors, layout, etc. In web page layout, setting the height of elements is also a commonly used technique. This article details how to use CSS to set the height of an element.
1. Method of setting element height
- Use px unit
Use CSS height attributeheight, you can set it by The height of the element controls the page layout. Among them, the most common unit is pixels (px), for example:
div {
height: 200px;
}
The above code means to set the height of the <div> element to 200 pixels, so that you can set the element by height to adjust the layout of the page.
- Use percentage units
In addition to pixel units, you can also use percentage units, for example:
div {
height: 50%;
}
The above code means that < The height of the div> element is set to 50% of the container in which it is located. For example, if the height of the container is 400 pixels, then the height of the <div> element is 200 pixels. This method is often used in responsive layouts to automatically adjust the height of elements based on the size of the container.
- Use vh unit
In addition to pixels and percentages, you can also use the window height (vh) as the unit. This method is similar to percentage, but is not affected by the width of the container. For example:
div {
height: 50vh;
}
The above code means to set the height of the <div> element to 50% of the height of the viewport, which occupies half of the screen height.
- Use em or rem units
In some cases, you can also use em or rem units to set the element height. Both units are relative units, em is the font size relative to the current element, and rem is the font size relative to the root element (that is, the <html> element). For example:
div {
height: 2em;
}
The above code means to set the height of the <div> element to twice the current font size. If the current element's font size is 14 pixels, the height of the <div> element will be 28 pixels.
2. Notes
- Height calculation method
When calculating the height of an element, pay attention to the box model of the element: Element The height includes content height, padding height and border height. If the box-sizing: border-box attribute is set, the element height includes the height of the padding and border, and the content height is the remaining space.
- Height restrictions
The height of some elements cannot be set through CSS, such as inline elements (inline) and display: none elements. In addition, the height of the parent element may also affect the height of the child elements. Pay attention to check whether the parent element limits the height of the child elements. If the height of the child element exceeds the height of the parent element, scroll bars will appear on the child element.
- Compatibility issues
When using height units, pay attention to compatibility issues: some browsers may not support certain units. For example, IE8 and below do not support the vh and rem units. In addition, different browsers may parse the same unit in different ways, and compatibility needs to be handled.
3. Summary
In this article, we introduced several methods to use CSS to set the height of elements, including pixels, percentages, window heights and relative units. When using these methods, you need to pay attention to the element's box model, height restrictions, and compatibility issues. At the same time, it is also necessary to select the most appropriate height unit according to specific needs to achieve the best page layout effect.
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