问题
Possible Duplicates:
Can someone explain the dollar sign in Javascript?
Why would a javascript variable start with a dollar sign?
Why is it that I can assign a function to $ in Javascript, but not # or ^ ?
回答1:
From the ECMA standard (Section 7.6)
The dollar sign ($) and the underscore (_) are permitted anywhere in an IdentifierName.
回答2:
The reason is because JavaScript is part of the ECMA-262 standard.
If you read section 7.6 you'll see the part about Identifier syntax.
Essentially the characters that can be used are defined by:
Identifier ::
IdentifierName but not ReservedWord
IdentifierName ::
IdentifierStart
IdentifierName IdentifierPart
IdentifierStart ::
UnicodeLetter
$
_
\
UnicodeEscapeSequence
IdentifierPart ::
IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
回答3:
If I understand your question, it's simply because the Javascript interpreter ignores $ as any type of special character. You can assign a function to a and you can assign one to $.
Much like an underscore, it treats $ as any "normal" character.
回答4:
Because that is what ECMA-262 specifies (see section 7.6)
Identifiers must match this RegEx: [a-zA-Z_$][0-9a-zA-Z_$]*
来源：https://stackoverflow.com/questions/4795551/why-is-a-valid-function-identifier