2.1.3 Unicode Escape Sequences
special sequences of six ASCII characters to represent any 16-bit Unicode codepoint.
These Unicode escapes begin with the characters \u and are followed by exactly four
hexadecimal digits (using uppercase or lowercase letters A–F). Unicode escapes may
not in language keywords). The Unicode escape for the character é, for example, is
"café" === "caf\u00e9" // => true
Unicode escapes may also appear in comments, but since comments are ignored, they
are treated as ASCII characters in that context and not interpreted as Unicode.