The support for the
getPropertyCSSValue method on the
CSSStyleDeclaration interface is now considered deprecated and will be removed in the near future. Firefox 61 and later will show a console warning for the method that has been classified as obsolete since 2003. Google Chrome has already removed the support back in 2014. Use the
getPropertyValue method instead.
Update: The method has been disabled on the Nightly channel as of Firefox 61.
Update 2: The method has been disabled also on Firefox Beta and Developer Edition as of Firefox 61.
Update 3: The method has been completely removed with Firefox 62.