Understanding and rationally utilizing the weighting mechanism of selectors is the key to solving the CSS style coverage problem, rather than relying on !important or inline styles. 1. Specificity consists of four types of weights, including ID, class/attribute/pseudo-class, element/pseudo-element selector, etc., and these weights determine the final style rules; 2. Use BEM naming specifications to reduce specific conflicts caused by nesting and improve maintainability; 3. Reasonably organize hierarchical structures, avoid deep nesting, and give priority to using a single class name to define styles; 4. Modern CSS provides @layer and :where() tools to more finely control the cascade order, help alleviate the style confusion problem in large projects.

In CSS development, overwriting styles and handling selector specificity are common challenges. You may encounter situations where you write a bunch of styles but don't work, and the problem is often the priority of the selector. The key to solving this problem is to understand and rationally utilize the weight mechanism of the selector, rather than just forcibly covering it with !important or inline styles.

Understand the specific rules of CSS selectors

Each selector in CSS has a calculated "specific value", and the browser will decide which style rule will eventually take effect based on this value. Specificity consists of four types of weights: !important , inline style, ID selector, class/attribute/pseudo-class selector, element/pseudo-element selector.

For example:

 /* Specificity is 0,1,0 */
div {
  color: red;
}

/* Specificity is 0,1,1 */
.container p {
  color: blue;
}

In the example above, .container p has higher specificity, so the paragraph text color will be blue. Understanding these rules helps us write more controllable styles and avoid unnecessary conflicts.

Use BEM or similar naming methods to reduce complexity

Using naming specifications like BEM (Block Element Modifier) ??can help you write class names with clear structure and strong maintenance, and reduce specific problems caused by nesting.

for example:

 <div class="card">
  <div class="card__title">Title</div>
  <div class="card__content card__content--highlighted">Content</div>
</div>

This naming method keeps relatively independent between classes, reducing nested selectors that rely on parent structures, thereby reducing the probability of style conflicts and making it easier to overwrite styles.

Reasonably organize CSS hierarchy to avoid excessive nesting

Sometimes we habitually write selectors like .sidebar ul li a , but this type of deeply nested selector not only increases specificity, but may also make it difficult to cover later.

Suggested practices include:

• Try to use a single class name to define styles
• Avoid nesting above three layers (especially in preprocessors such as SCSS)
• Manage common styles and component styles separately, such as CSS-in-JS or modular CSS

If you really need to raise the priority of a certain style, consider copying the original selector and expanding it appropriately instead of simply adding !important .

Use cascading order tools when necessary, such as @layer and :where()

Modern CSS provides some new features to help us better control the order of cascade:

• @layer allows you to define style sheets at different levels and control the priority between them.
• :where() is a zero-specific selector suitable for reset or default style settings.

Example:

 :where(.button) {
  padding: 10px;
}

/* Specificity is 0,0,1, but it is equivalent to 0,0,0 in actual application */

Although these tools are not necessary, they can effectively alleviate the confusion caused by style coverage in large projects.

Basically that's it. Covering styles is not a master skill, but to do it neatly, you need to have a clear understanding of the weight of the selector and work hard on project structure and naming strategies.

The above is the detailed content of What are the best practices for overriding styles and managing specificity in CSS Selectors?. For more information, please follow other related articles on the PHP Chinese website!