<p> The inheritance and casing mechanism of CSS is a very basic but easily overlooked part of front-end development. When many people write styles, they find that some styles are not effective or are covered by other styles. The problem is often due to the lack of understanding of inheritance and casing. This article does not go around the corner, but focuses on the key points.
What is CSS inheritance?
<p> Not all CSS attributes are automatically "passed" to child elements, but some of them will. For example, text-related attributes such as font, color, and line height will be inherited by child elements by default.
<p> For example:<div class="parent"> <p>This text will inherit the parent's text color</p> </div>
.parent {
color: blue;
}<p> In the example above, the <p> tag does not have a color set, but it displays blue because color attribute is inheritable. 
<p> But layout class attributes such as border , margin , and padding will not be inherited. If you want the child elements to use these values, you have to write them explicitly yourself.<p> Common inheritable attributes include:-
color -
font-family,font-size,font-weight -
text-align,text-transform -
line-height -
visibility
How does the casing mechanism work?
<p> Cascade is the process by which the browser decides which CSS rules to use. Multiple rules may match an element at the same time, so who should I listen to? Here are a few key points:- Source priority: User Agent Style < User Style < Developer Style (that is, what you wrote)
- Importance:
!importantrules have higher priority, but are not recommended for abuse. - Specificity: ID > Class/Attribute Selector > Tag Selector
- Order: The same specific rules, the following will cover the previous one
p {
color: red;
}
.content p {
color: green;
}<p> Even if both match <p> , .content p is more specific, so the text is green.
Several common pitfalls in actual development
- <p> Global style pollution
When using a universal selector (such as*orbody *), elements that should not be affected may be accidentally affected, especially content in third-party component libraries. - <p> Side effects of inheritance
For example, ifhtml { font-size: 16px; }is set, and then a child element usesemorrem, the calculated size is not expected. Debugging this kind of problem is a bit troublesome, but as long as you understand the inheritance chain, it is not difficult to solve. - <p> The cascading order causes the style to not take effect
It is common when multiple frameworks or components are mixed, such as Tailwind and custom CSS exist at the same time. At this time, you can use the browser developer tools to check which rules are applied and adjust the specificity of the selector.
How to handle inheritance and casing more efficiently?
- Try to avoid using
!important, unless it is special, it can complicate maintenance. - Use BEM or similar naming specifications to improve the readability and specific control of class names.
- Reasonably organize the CSS file structure , separate reset styles, basic styles, component styles, and theme styles to reduce conflicts.
- Make good use of the Computed panel of browser developer tools to see which rules finally take effect.
<p> Basically that's it. Inheritance and casing don't seem complicated, but it can easily become the culprit of "why my style doesn't work" in real projects. If you understand the logic behind these mechanisms, you can avoid many pitfalls when writing styles.
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