http://www.ecma-international.org/ecma-262/5.1/#sec-7.6
Identifier Names are tokens that are interpreted according to the grammar given in the “Identifiers” section of chapter 5 of the Unicode standard, with some small modifications. An Identifier is an IdentifierName that is not a ReservedWord
标识符名是tokens,Unicode 标准第5 章的“标识符”节给出的文法加入了一些小的修改来解释它。Identifier 是一个IdentifierName 但不是一个ReservedWord
知道不是ReservedWord就可以。