标识符ecmascript 2017规范

Question

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"?

Answer 1

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.