CSSRule

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.

Syntax

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

CSSRule.cssText

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.

Constants

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:

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.

Specifications

Browser compatibility

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

See also

• Using dynamic styling information