如果正则表达式不是必须的，最好是让浏览器决定使用eval:

function isValidVarName( name ) {
    try {
        // Update, previoulsy it was
        // eval('(function() { var ' + name + '; })()');
        Function('var ' + name);
    } catch( e ) {
        return false;
    }
    return true;
}

isValidVarName('my_var');     // true
isValidVarName('1');          // false

下面是创建变量名的一个快速建议。

如果您希望变量在Firefox中使用时不发生冲突，请不要使用变量名“_content”，因为该变量名已被浏览器使用。我发现这一点很困难，不得不在一个大型JavaScript应用程序中更改所有使用变量“_content”的地方。

在ECMAScript规范第7.6节的标识符名称和标识符中，一个有效的标识符定义为:

Identifier ::
    IdentifierName but not ReservedWord

IdentifierName ::
    IdentifierStart
    IdentifierName IdentifierPart

IdentifierStart ::
    UnicodeLetter
    $
    _
    \ UnicodeEscapeSequence

IdentifierPart ::
    IdentifierStart
    UnicodeCombiningMark
    UnicodeDigit
    UnicodeConnectorPunctuation
    \ UnicodeEscapeSequence

UnicodeLetter
    any character in the Unicode categories “Uppercase letter (Lu)”, “Lowercase letter (Ll)”, “Titlecase letter (Lt)”,
    “Modifier letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.

UnicodeCombiningMark
    any character in the Unicode categories “Non-spacing mark (Mn)” or “Combining spacing mark (Mc)”

UnicodeDigit
    any character in the Unicode category “Decimal number (Nd)”

UnicodeConnectorPunctuation
    any character in the Unicode category “Connector punctuation (Pc)”

UnicodeEscapeSequence
    see 7.8.4.

HexDigit :: one of
    0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F

这为命名变量创造了很多机会，在高尔夫运动中也是如此。我们来举几个例子。

有效的标识符可以以UnicodeLetter、$、_或\ UnicodeEscapeSequence开头。Unicode字母是以下类别中的任何字符(请参阅所有类别):

大写字母(Lu) 小写字母(Ll) 头衔信(Lt) 修饰字母(Lm) 其他字母(Lo) 字母编号(Nl)

仅这一点就说明了一些疯狂的可能性-工作的例子。如果它不能在所有浏览器中工作，那么就称它为bug，因为它应该是bug。

var ᾩ = "something";
var ĦĔĽĻŎ = "hello";
var 〱〱〱〱 = "less than? wtf";
var जावास्क्रिप्ट = "javascript"; // OK, that's JavaScript in Hindi
var KingGeorgeⅦ = "Roman numerals, awesome!";

引用有效的JavaScript变量名，我的文章总结了相关的规范部分:

An identifier must start with $, _, or any character in the Unicode categories “Uppercase letter (Lu)”, “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”. The rest of the string can contain the same characters, plus any U+200C zero width non-joiner characters, U+200D zero width joiner characters, and characters in the Unicode categories “Non-spacing mark (Mn)”, “Spacing combining mark (Mc)”, “Decimal digit number (Nd)”, or “Connector punctuation (Pc)”.

我还创建了一个工具，可以告诉你输入的任何字符串是否符合ECMAScript 5.1和Unicode 6.1的有效JavaScript变量名:

注:为了让您了解Anthony Mills的回答有多错误:如果您将所有这些规则总结为JavaScript的一个ascii正则表达式，那么它将有11,236个字符长。下面就是:

// ES5.1 / Unicode 6.1
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基本上，以正则表达式形式:[a-zA-Z_$][0-9a-zA-Z_$]*。换句话说，第一个字符可以是字母、_或$，其他字符可以是字母、_、$或数字。

注意:虽然其他回答指出可以在JavaScript标识符中使用Unicode字符，但实际的问题是“我应该使用什么字符作为像jQuery这样的扩展库的名称?”这就是那个问题的答案。您可以在标识符中使用Unicode字符，但不要这样做。编码总是被搞砸。将公共标识符保持在32-126 ASCII范围内，这样比较安全。

如果正则表达式不是必须的，最好是让浏览器决定使用eval:

function isValidVarName( name ) {
    try {
        // Update, previoulsy it was
        // eval('(function() { var ' + name + '; })()');
        Function('var ' + name);
    } catch( e ) {
        return false;
    }
    return true;
}

isValidVarName('my_var');     // true
isValidVarName('1');          // false