id property

The id property of the Element interface represents the element's identifier, reflecting the id global attribute.

If the id value is not the empty string, it must be unique in a document.

The id is often used with Document.getElementById to retrieve a particular element. Another common case is to use an element's ID as a selector when styling the document with CSS.

Note: Identifiers are case-sensitive, but you should avoid creating IDs that differ only in the capitalization.