Fix set property invalid description of priority parameter

[OlaviSau]

Description

This change corrects the parameter description for CSSStyleDeclaration setProperty method.

Motivation

These changes reflect the full list of accepted values and more accurately describe what happens when an invalid value is passed.

Additional details

Related issues and pull requests

• I am not sure if there are related issues.

[github-actions]

Preview URLs

• /en-US/docs/Web/API/CSSStyleDeclaration/setProperty

(comment last updated: 2025-03-22 18:15:29)

[Josh-Cena]

Sure, thanks

[OlaviSau]

@Josh-Cena If the value is empty and the priority is invalid, no change will be applied even if the value is empty, so the changed description is invalid. Verified on chrome / firefox.
Thus "unless value is empty, in which case the property is removed regardless of the priority value" is not valid.

[Josh-Cena]

@OlaviSau It works on Firefox. To try this, open the live example on this page. Change the stylesheet line to const stylesheet = document.styleSheets[2]; (an annoying bug: mdn/yari#12809) and change the setRandomBorder function to:

function setRandomBorder() {
  boxParaRule.style.setProperty("border", "", "foo");
}

And press the "border" button. You will see that the border disappears.

The algorithm in the spec: https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-setproperty also says if value is empty then priority is not validated at all.

That it does not work in Chrome or Safari may be a bug to be reported to these browsers, but Firefox is the only compliant browser for now.