Firefox 78 Released, Enables CSS :is and :where Selectors

Firefox 78 was released on 30th June, 2020. Major web platform updates in this version include :

• CSS :is() and :where() pseudo-classes are enabled. Both these are useful for writing large selectors in a more concise form.

  /* old way */
  header p,
  main p,
  footer p {
  	color: red;
  }
  
  /* new way using :is() */
  :is(header, main, footer) p {
  	color: red;
  }
  

  :is() and :where() differ in specificity.

• New features have been added to Javascript regular expressions as per ES2018 :
  • Lookbehind assertions — basically a regular expression can read backwards for a match
  • dotAll property — that indicates whether or not "s" flag in used in the regex
  • Unicode property escapes — for allowing character matching based on Unicode
  • Named capture groups — basically names can be specified for returned matches in a group
• replaceChildren() DOM method has been implemented. Like the name suggests, this replaces existing children of a DOM Node with new set of child nodes.
• Intl.ListFormat API is supported
• And more

Read the full Mozilla blog post.