The @supports
rule's ability to check for selector support is surprisingly robust! While often used to test for property: value
pair compatibility, the selector()
function extends its capabilities to evaluate selector support. This is done by simply placing the selector within the parentheses:
@supports selector(:nth-child(1 of .foo)) { /* Styles applied if the selector is supported */ }
The :nth-child(n of .foo)
selector, a "selector list argument" compatible with :nth-child
family selectors, serves as a good example. Currently, only Safari supports this specific selector.
Consider a scenario where you need to style a list with separators and zebra striping. Ideally, you'd use a selector like this to achieve the zebra striping while ignoring separators:
li:nth-child(odd of .list-item) { background: lightgoldenrodyellow; }
However, due to limited browser support, you can use @supports
to conditionally apply this style:
@supports selector(:nth-child(1 of .foo)) { li { padding: 0.25em; } li:nth-child(odd of .list-item) { background: lightgoldenrodyellow; } li.separator { list-style: none; margin: 0.25em 0; } } @supports not selector(:nth-child(1 of .foo)) { li.separator { height: 1px; list-style: none; border-top: 1px dashed purple; margin: 0.25em 0; } }
This provides a fallback style for browsers lacking support for the advanced selector. An improved syntax, potentially using @when
and @else
, could simplify this:
/* Hypothetical future syntax */ @when supports(selector(:nth-child(1 of .foo))) { /* Styles for supporting browsers */ } @else { /* Fallback styles */ }
A JavaScript API also exists for testing selector support:
CSS.supports("selector(:nth-child(1 of .foo))")
This method returns true
in Safari and false
in Chrome (at the time of writing).
While the @supports
rule is powerful, the number of CSS selectors with inconsistent cross-browser support, and the number of use cases requiring @supports
for those selectors, is relatively small. Many previously problematic selectors, such as ::marker
and case-insensitive attribute selectors, now enjoy broad support. Selectors like :fullscreen
or :-webkit-full-screen
might offer interesting and useful applications due to their unique lack of support in iOS Safari.
The above is the detailed content of @supports selector(). For more information, please follow other related articles on the PHP Chinese website!

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