An object implementing the CSSRule DOM interface represents a single CSS at-rule. References to a CSSRule-implementing object may be obtained by looking at a CSS style sheet's cssRules list.

    There are several kinds of rules. The CSSRule interface specifies the properties common to all rules, while properties unique to specific rule types are specified in the more specialized interfaces for those rules' respective types.


    The syntax is described using the WebIDL format.

    interface CSSRule {
        const unsigned short STYLE_RULE = 1;
        const unsigned short CHARSET_RULE = 2;
        const unsigned short IMPORT_RULE = 3;
        const unsigned short MEDIA_RULE = 4;
        const unsigned short FONT_FACE_RULE = 5;
        const unsigned short PAGE_RULE = 6;
        const unsigned short KEYFRAMES_RULE = 7;
        const unsigned short KEYFRAME_RULE = 8;
        const unsigned short NAMESPACE_RULE = 10;
        const unsigned short COUNTER_STYLE_RULE = 11;
        const unsigned short SUPPORTS_RULE = 12;
        const unsigned short DOCUMENT_RULE = 13;
        const unsigned short FONT_FEATURE_VALUES_RULE = 14;
        const unsigned short VIEWPORT_RULE = 15;
        const unsigned short REGION_STYLE_RULE = 16;
        readonly attribute unsigned short type;
        attribute DOMString cssText;
        readonly attribute CSSRule? parentRule;
        readonly attribute CSSStyleSheet? parentStyleSheet;

    Properties common to all CSSRule instances

    Represents the textual representation of the rule, e.g. "h1,h2 { font-size: 16pt }"
    CSSRule.parentRule 只读
    Returns the containing rule, otherwise null. E.g. if this rule is a style rule inside an @media block, the parent rule would be that CSSMediaRule.
    CSSRule.parentStyleSheet 只读
    Returns the CSSStyleSheet object for the style sheet that contains this rule
    CSSRule.type 只读
    One of the Type constants indicating the type of CSS rule.


    Type constants

    The CSSRule interface specifies integer constants that can be used in conjunction with a CSSRule's type property to discern the rule type (and therefore, which specialized interface it implements). The relationships between these constants and the interfaces are:

    Type Value Rule-specific interface
    CSSRule.STYLE_RULE 1 CSSStyleRule
    CSSRule.MEDIA_RULE 4 CSSMediaRule
    CSSRule.FONT_FACE_RULE 5 CSSFontFaceRule
    CSSRule.PAGE_RULE 6 CSSPageRule
    CSSRule.IMPORT_RULE 3 CSSImportRule : IDL: nsIDOMCSSImportRule
    CSSRule.CHARSET_RULE 2 CSSCharsetRule
    CSSRule.UNKNOWN_RULE 0 CSSUnknownRule
    CSSRule.KEYFRAMES_RULE 7 CSSKeyframesRule [1]
    CSSRule.KEYFRAME_RULE 8 CSSKeyframeRule [1]
    Reserved for future use 9 Should be used to define color profiles in the future
    CSSRule.NAMESPACE_RULE 10 CSSNamespaceRule
    CSSRule.COUNTER_STYLE_RULE 11 CSSCounterStyleRule
    CSSRule.SUPPORTS_RULE 12 CSSSupportsRule
    CSSRule.DOCUMENT_RULE 13 CSSDocumentRule
    CSSRule.FONT_FEATURE_VALUES_RULE 14 CSSFontFeatureValuesRule
    CSSRule.VIEWPORT_RULE 15 CSSViewportRule
    CSSRule.REGION_STYLE_RULE 16 CSSRegionStyleRule

    An up-to-date informal list of constants can be found on the CSSWG Wiki.

    [1] On Gecko, before Firefox 19, the keyframe-related constants existed only in their prefixed version: CSSRule.MOZ_KEYFRAMES_RULE and CSSRule.MOZ_KEYFRAME_RULE. From Firefox 20 onwards, both versions are available. The prefixed version will be removed in the future.


    Specification Status Comment
    CSS Object Model (CSSOM)
    Working Draft Obsoleted values CHARSET_RULE and UNKNOWN_RULE. Added value NAMESPACE_RULE.
    CSS Animations
    Working Draft Added values KEYFRAMES_RULE and KEYFRAME_RULE.
    CSS Fonts Module Level 3
    Candidate Recommendation Added value FONT_FEATURE_VALUES_RULE.
    CSS Counter Styles Level 3
    Working Draft Added value COUNTER_STYLE_RULE.
    CSS Conditional Rules Module Level 3
    Candidate Recommendation Added value SUPPORTS_RULE. (DOCUMENT_RULE has been pushed to CSS Conditional Rules Level 4)
    Document Object Model (DOM) Level 2 Style Specification
    Recommendation Initial definition.

    Browser compatibility

    To get browser compatibility information about the different type constant value, please consult the compatibility table of the associated interface.

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support (Yes) (Yes) 9 (Yes) (Yes)
    Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes)

    See also


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