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Identifier ecmascript 2017 specification

Hello from ecmascript specifications

UnicodeIDStart::
   any Unicode code point with the Unicode property "ID_Start"
UnicodeIDContinue::
   any Unicode code point with the Unicode property "ID_Continue"

What are the the Unicode property "ID_Start" and "ID_Continue"?

Solution

  • It refers to Unicode character properties. As the ES spec says

    IdentifierName and ReservedWord are tokens that are interpreted according to the Default Identifier Syntax given in Unicode Standard Annex #31, Identifier and Pattern Syntax […]. The Unicode identifier grammar is based on character properties specified by the Unicode Standard.

    That standard is also referenced in the bibliography of the spec.