CSSFunctionDescriptors
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The CSSFunctionDescriptors interface of the CSS Object Model represents the descriptors contained within a set of CSS declarations represented by a CSSFunctionDeclarations object.
A CSSFunctionDescriptors object is accessed via the CSSFunctionDeclarations.style property.
Instance properties
This interface also inherits properties from CSSRule.
CSSFunctionDescriptors.resultRead only Experimental-
Returns a string representing a
resultdescriptor, if one exists in the associated set of declarations.
Examples
Basic CSSFunctionDescriptors usage
In this example, we define a CSS custom function and then access its declarations using the CSSOM.
CSS
Our CSS defines a custom function using the @function at-rule. The function is called --lighter(), and outputs a lightened version of an input color. --lighter() accepts two parameters, a <color> and a <number>. It returns an oklch() color created using relative color syntax; the input color is transformed into an oklch() color and its lightness channel is increased by the input number.
@function --lighter(--color <color>, --lightness-adjust <number>: 0.2) returns
<color> {
result: oklch(from var(--color) calc(l + var(--lightness-adjust)) c h);
}
JavaScript
Our script starts by getting a reference to the stylesheet attached to our document using HTMLStyleElement.sheet, then getting a reference to the only rule in the stylesheet, the CSSFunctionRule — via CSSStylesheet.cssRules.
We then access the CSSFunctionDeclarations object representing the only continuous run of declarations inside the function using cssRules[0], access its descriptor's information using CSSFunctionDeclarations.style, and then access the descriptor style information. All of this information is logged to the console.
// Get a CSSFunctionRule
const cssFunc = document.getElementById("css-output").sheet.cssRules[0];
// Accessing CSSFunctionDeclarations and CSSFunctionDescriptors
console.log(cssFunc.cssRules[0]); // CSSFunctionDeclarations
console.log(cssFunc.cssRules[0].style); // CSSFunctionDescriptors
console.log(cssFunc.cssRules[0].style.result);
Most notably, the result property is equal to the @function body's result descriptor, which is oklch(from var(--color) calc(l + var(--lightness-adjust)) c h).
Specifications
| Specification |
|---|
| CSS Functions and Mixins Module # cssfunctiondescriptors |
Browser compatibility
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