据我所知，公认的答案将排除许多有效的标识符。下面是一个符合规范的正则表达式(参见7.6章关于标识符)。使用RegexBuddy创建它，您可以在http://samples.geekality.net/js-identifiers上找到解释的导出。

^[$_\p{L}][$_\p{L}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\u200C\u200D]*+$

且名称不能为以下保留字。

Break, do, instanceof, typeof, case, else, new, var, catch, finally, return, void, continue, for, switch, while, debugger, function, this, with, default, if, throw, delete, in, try, class, enum, extends, super, const, export, import, implements, let, private, public, yield, interface, package, protected, static, null, true, false

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。

JavaScript变量

可以用任意字母、$或_字符作为变量的开头。只要不是以数字开头，你也可以包含数字。

开始:[a-z]， $， _

包含:[a-z]， [0-9]， $， _

jQuery

你可以在你的库中使用_，这样它就可以和jQuery并肩作战了。但是，可以设置一个配置，使jQuery不使用$。它将使用jQuery。要做到这一点，只需设置:

jQuery.noConflict();

本页解释了如何做到这一点。

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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我写了一个小故障工作空间，迭代所有的代码点，并在eval('var ' + String.fromCodePoint(#) + ' = 1')工作时发出字符。

它一直在继续，继续，继续....

我采纳了Anas Nakawa的想法并加以改进。首先，没有理由实际运行被声明的函数。我们想知道它是否正确地解析，而不是代码是否工作。其次，对于我们的目的来说，文字对象是一个比var XXX更好的上下文，因为它更难摆脱。

    function isValidVarName( name ) {
    try {
        return name.indexOf('}') === -1 && eval('(function() { a = {' + name + ':1}; a.' + name + '; var ' + name + '; }); true');
    } catch( e ) {
        return false;
    }
    return true;
}

// so we can see the test code
var _eval = eval;
window.eval = function(s) {
    console.log(s);
    return _eval(s);
}

console.log(isValidVarName('name'));
console.log(isValidVarName('$name'));
console.log(isValidVarName('not a name'));
console.log(isValidVarName('a:2,b'));
console.log(isValidVarName('"a string"'));

console.log(isValidVarName('xss = alert("I\'m in your vars executin mah scrip\'s");;;;;'));
console.log(isValidVarName('_;;;'));
console.log(isValidVarName('_=location="#!?"'));

console.log(isValidVarName('ᾩ'));
console.log(isValidVarName('ĦĔĽĻŎ'));
console.log(isValidVarName('〱〱〱〱'));
console.log(isValidVarName('जावास्क्रिप्ट'));
console.log(isValidVarName('KingGeorgeⅦ'));
console.log(isValidVarName('}; }); alert("I\'m in your vars executin\' mah scripts"); true; // yeah, super valid'));
console.log(isValidVarName('if'));