使用通用選擇器在CSS中確實有性能影響，尤其在大型網(wǎng)站或複雜頁面上。選擇器會匹配頁面上的每一個元素，包括、
及所有子元素和偽元素，導(dǎo)致瀏覽器檢查每個DOM節(jié)點是否應(yīng)用樣式，增加渲染工作量。常見用途如全局重置樣式或設(shè)置box-sizing，但這些規(guī)則會應(yīng)用於不必要的元素，增加冗餘計算。在大型頁面或低端設(shè)備上，性能損耗更明顯。優(yōu)化方法是僅針對需要的元素設(shè)置樣式而非使用。但在小型網(wǎng)站、原型開發(fā)或調(diào)試時，其性能影響可忽略不計，此時使用反而更高效?？傮w而言，在生產(chǎn)環(huán)境或大規(guī)模站點中應(yīng)限制*的使用以提升性能。
Using the universal selector * in CSS can have performance implications, especially on large websites or complex pages. While it's not something most developers need to worry about in small projects, understanding how and when it affects rendering can help you make better decisions.
How the Universal Selector Works
The * selector targets every single element on a webpage. That includes everything from and down to each <div> , <code><span></span> , and even pseudo-elements if used with them.
This broad targeting means the browser has to check every DOM node for matching styles, which can add up quickly. On a page with thousands of elements (like those found in dashboards or data-heavy apps), this can cause unnecessary work during rendering.
- It applies styles to more elements than needed.
- It increases the number of style recalculations during layout changes.
In short: the broader your selector, the more work the browser must do.
Common Use Cases and Their Impact
Developers often use * for resetting margins and paddings or setting global box-sizing:
* {
margin: 0;
padding: 0;
box-sizing: border-box;
} While convenient, these rules apply to every element, even those that don't need them. For example, applying box-sizing: border-box to an element like <html> doesn't hurt, but it's redundant.
Here's where performance starts to matter:
- Large pages with many nested or dynamically added elements will see a larger performance hit.
- Mobile devices or lower-end hardware might experience slower rendering due to extra computation.
Instead of using * , consider targeting only what you need:
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby??, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
box-sizing: border-box;
}It looks messy, but limits the scope to just common HTML elements — skipping less-used ones.
When It's Safe to Use *
Despite its drawbacks, there are cases where using * is perfectly fine:
- Small websites or landing pages with fewer than 100 elements.
- Prototyping or early-stage development where speed matters more than optimization.
- Specific visual effects like outlining all elements for debugging:
* {
outline: 1px solid red;
}In these scenarios, the performance cost is negligible, and the convenience of writing shorter CSS wins out.
Still, once you move into production or scale up your site, it's worth revisiting these global rules and trimming unnecessary selectors.
Performance concerns around * aren't dramatic in most cases, but they're real. If your site grows large or needs to run smoothly across all devices, avoiding the universal selector — or at least limiting its use — is a good habit to build.
以上是使用通用選擇器 *的性能含義是什麼？的詳細(xì)內(nèi)容。更多資訊請關(guān)注PHP中文網(wǎng)其他相關(guān)文章！
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