Identifier

An identifier is a sequence of characters in the code that identifies a variable, function, or property. In most languages, identifiers are case-sensitive and not quoted.

In JavaScript, identifiers can contain Unicode letters, $, _, and digits (0-9), but may not start with a digit. An identifier differs from a string in that a string is data, while an identifier is part of the code. In JavaScript, there is no way to convert identifiers to strings, but sometimes it is possible to parse strings into identifiers.

In CSS, there are two identifier data types: <custom-ident> and <dashed-ident>. The CSS <ident> can contain almost any character, but non-letter/digit ASCII characters such as ", \, and * must be escaped, it must not start with a digit, and emojis are valid as identifiers that do not require escaping.