在Javascript的ECMAScript语法规范中,有双冒号定义的块如下:
Literal ::
NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
RegularExpressionLiteral
并且像这样只使用一个冒号定义的块:
PrimaryExpression :
this
Identifier
Literal
ArrayLiteral
ObjectLiteral
( Expression )
而且,即使是带有三个冒号的块:
uriCharacter :::
uriReserved
uriUnescaped
uriEscaped
单冒号、双冒号和三冒号有什么区别?