为什么不是◎ܫ◎和☺有效的JavaScript变量名？
我注意到在Internet Explorer中（但不幸的是，在我测试过的其他浏览器中），可以使用一些Unicode变量名称。 这让我感到很开心，我非常高兴能够编写出如此有趣的支持Unicode的代码：
var ктоείναι草泥马 = "You dirty horse.",
happy☺n☺mat☺p☺eia = ":)Yay!",
ಠ_ಠ = "emoticon";
alert(ктоείναι草泥马 + happy☺n☺mat☺p☺eia + ಠ_ಠ);
不过，由于某些原因， ◎ܫ◎ ， ♨_♨和☺不是有效的变量名称。
ಠ_ಠ和草泥马为什么要工作，但◎ܫ◎ ， ♨_♨和☺不工作？
编辑：在JSFiddle的浏览器中进行测试。 我已经在Internet Explorer 9，Chrome，Firefox和Opera上测试过它。 到目前为止，它似乎只适用于Internet Explorer 9（我不知道Internet Explorer 8及以下版本。）让我知道它是否适用于其他浏览器。
ಠ_ಠ和草泥马只包含实际字母中使用的“字母”; 即ಠ是来自卡纳达语字母的符号，草泥马由汉字组成。
然而，◎和are纯粹是符号; 他们不与任何字母表相关联。
ECMAScript标准第7.6章（除Internet Explorer以外的所有浏览器都遵循）指出，标识符必须以下列之一开头。
$或_ 标识符的以下字符必须是下列之一。
IE超越了标准，并且允许一些符号，如☺。
根据ECMAScript 5.1和Unicode 6.1，有一个工具可以告诉您输入的任何字符串是否为有效的JavaScript变量名称。
EcmaScript 262第7.6节说，名称必须以$，_或Unicode字母开头，之后可能包含这些字符或Unicode组合标记，Unicode数字或Unicode连接符号（以及一些格式控制字符是语言特定的。）
因此，您的案例中允许和不允许标识符之间的区别可能在于主角是否被视为“字母”。
为了引用有效的JavaScript变量名称 ，我撰写了总结相关规范部分的文章：
标识符必须以$ ， _或Unicode类别中的任何字符开头：“大写字母（Lu）”，“小写字母（Ll）”，“标题字母（Lt）”，“修饰符字母（Lm）”，“其他字母（Lo）“或”字母编号（Nl）“。
字符串的其余部分可以包含相同的字符，以及任何U + 200C零宽度非连接字符，U + 200D零宽度连接符字符以及Unicode类别中的字符“非间距标记（Mn）”，“间距组合标记（Mc）“，”十进制数字号码（Nd）“或”连接器标点符号（Pc）“。
我还创建了一个工具，它可以告诉您输入的任何字符串是否符合ECMAScript 5.1和Unicode 6.3的有效JavaScript变量名称：
PS如果您要将所有这些规则汇总为JavaScript的单一ASCII纯正则表达式， 则其长度将超过9000个字符 。 这里是：
// ECMAScript 5.1 / Unicode v6.3.0:
/^(?!(?:do|if|in|for|let|new|try|var|case|else|enum|eval|null|this|true|void|with|break|catch|class|const|false|super|throw|while|yield|delete|export|import|public|return|static|switch|typeof|default|extends|finally|package|private|continue|debugger|function|arguments|interface|protected|implements|instanceof)$)[x24A-Zx5Fa-zxAAxB5xBAxC0-xD6xD8-xF6xF8-u02C1u02C6-u02D1u02E0-u02E4u02ECu02EEu0370-u0374u0376u0377u037A-u037Du0386u0388-u038Au038Cu038E-u03A1u03A3-u03F5u03F7-u0481u048A-u0527u0531-u0556u0559u0561-u0587u05D0-u05EAu05F0-u05F2u0620-u064Au066Eu066Fu0671-u06D3u06D5u06E5u06E6u06EEu06EFu06FA-u06FCu06FFu0710u0712-u072Fu074D-u07A5u07B1u07CA-u07EAu07F4u07F5u07FAu0800-u0815u081Au0824u0828u0840-u0858u08A0u08A2-u08ACu0904-u0939u093Du0950u0958-u0961u0971-u0977u0979-u097Fu0985-u098Cu098Fu0990u0993-u09A8u09AA-u09B0u09B2u09B6-u09B9u09BDu09CEu09DCu09DDu09DF-u09E1u09F0u09F1u0A05-u0A0Au0A0Fu0A10u0A13-u0A28u0A2A-u0A30u0A32u0A33u0A35u0A36u0A38u0A39u0A59-u0A5Cu0A5Eu0A72-u0A74u0A85-u0A8Du0A8F-u0A91u0A93-u0AA8u0AAA-u0AB0u0AB2u0AB3u0AB5-u0AB9u0ABDu0AD0u0AE0u0AE1u0B05-u0B0Cu0B0Fu0B10u0B13-u0B28u0B2A-u0B30u0B32u0B33u0B35-u0B39u0B3Du0B5Cu0B5Du0B5F-u0B61u0B71u0B83u0B85-u0B8Au0B8E-u0B90u0B92-u0B95u0B99u0B9Au0B9Cu0B9Eu0B9Fu0BA3u0BA4u0BA8-u0BAAu0BAE-u0BB9u0BD0u0C05-u0C0Cu0C0E-u0C10u0C12-u0C28u0C2A-u0C33u0C35-u0C39u0C3Du0C58u0C59u0C60u0C61u0C85-u0C8Cu0C8E-u0C90u0C92-u0CA8u0CAA-u0CB3u0CB5-u0CB9u0CBDu0CDEu0CE0u0CE1u0CF1u0CF2u0D05-u0D0Cu0D0E-u0D10u0D12-u0D3Au0D3Du0D4Eu0D60u0D61u0D7A-u0D7Fu0D85-u0D96u0D9A-u0DB1u0DB3-u0DBBu0DBDu0DC0-u0DC6u0E01-u0E30u0E32u0E33u0E40-u0E46u0E81u0E82u0E84u0E87u0E88u0E8Au0E8Du0E94-u0E97u0E99-u0E9Fu0EA1-u0EA3u0EA5u0EA7u0EAAu0EABu0EAD-u0EB0u0EB2u0EB3u0EBDu0EC0-u0EC4u0EC6u0EDC-u0EDFu0F00u0F40-u0F47u0F49-u0F6Cu0F88-u0F8Cu1000-u102Au103Fu1050-u1055u105A-u105Du1061u1065u1066u106E-u1070u1075-u1081u108Eu10A0-u10C5u10C7u10CDu10D0-u10FAu10FC-u1248u124A-u124Du1250-u1256u1258u125A-u125Du1260-u1288u128A-u128Du1290-u12B0u12B2-u12B5u12B8-u12BEu12C0u12C2-u12C5u12C8-u12D6u12D8-u1310u1312-u1315u1318-u135Au1380-u138Fu13A0-u13F4u1401-u166Cu166F-u167Fu1681-u169Au16A0-u16EAu16EE-u16F0u1700-u170Cu170E-u1711u1720-u1731u1740-u1751u1760-u176Cu176E-u1770u1780-u17B3u17D7u17DCu1820-u1877u1880-u18A8u18AAu18B0-u18F5u1900-u191Cu1950-u196Du1970-u1974u1980-u19ABu19C1-u19C7u1A00-u1A16u1A20-u1A54u1AA7u1B05-u1B33u1B45-u1B4Bu1B83-u1BA0u1BAEu1BAFu1BBA-u1BE5u1C00-u1C23u1C4D-u1C4Fu1C5A-u1C7Du1CE9-u1CECu1CEE-u1CF1u1CF5u1CF6u1D00-u1DBFu1E00-u1F15u1F18-u1F1Du1F20-u1F45u1F48-u1F4Du1F50-u1F57u1F59u1F5Bu1F5Du1F5F-u1F7Du1F80-u1FB4u1FB6-u1FBCu1FBEu1FC2-u1FC4u1FC6-u1FCCu1FD0-u1FD3u1FD6-u1FDBu1FE0-u1FECu1FF2-u1FF4u1FF6-u1FFCu2071u207Fu2090-u209Cu2102u2107u210A-u2113u2115u2119-u211Du2124u2126u2128u212A-u212Du212F-u2139u213C-u213Fu2145-u2149u214Eu2160-u2188u2C00-u2C2Eu2C30-u2C5Eu2C60-u2CE4u2CEB-u2CEEu2CF2u2CF3u2D00-u2D25u2D27u2D2Du2D30-u2D67u2D6Fu2D80-u2D96u2DA0-u2DA6u2DA8-u2DAEu2DB0-u2DB6u2DB8-u2DBEu2DC0-u2DC6u2DC8-u2DCEu2DD0-u2DD6u2DD8-u2DDEu2E2Fu3005-u3007u3021-u3029u3031-u3035u3038-u303Cu3041-u3096u309D-u309Fu30A1-u30FAu30FC-u30FFu3105-u312Du3131-u318Eu31A0-u31BAu31F0-u31FFu3400-u4DB5u4E00-u9FCCuA000-uA48CuA4D0-uA4FDuA500-uA60CuA610-uA61FuA62AuA62BuA640-uA66EuA67F-uA697uA6A0-uA6EFuA717-uA71FuA722-uA788uA78B-uA78EuA790-uA793uA7A0-uA7AAuA7F8-uA801uA803-uA805uA807-uA80AuA80C-uA822uA840-uA873uA882-uA8B3uA8F2-uA8F7uA8FBuA90A-uA925uA930-uA946uA960-uA97CuA984-uA9B2uA9CFuAA00-uAA28uAA40-uAA42uAA44-uAA4BuAA60-uAA76uAA7AuAA80-uAAAFuAAB1uAAB5uAAB6uAAB9-uAABDuAAC0uAAC2uAADB-uAADDuAAE0-uAAEAuAAF2-uAAF4uAB01-uAB06uAB09-uAB0EuAB11-uAB16uAB20-uAB26uAB28-uAB2EuABC0-uABE2uAC00-uD7A3uD7B0-uD7C6uD7CB-uD7FBuF900-uFA6DuFA70-uFAD9uFB00-uFB06uFB13-uFB17uFB1DuFB1F-uFB28uFB2A-uFB36uFB38-uFB3CuFB3EuFB40uFB41uFB43uFB44uFB46-uFBB1uFBD3-uFD3DuFD50-uFD8FuFD92-uFDC7uFDF0-uFDFBuFE70-uFE74uFE76-uFEFCuFF21-uFF3AuFF41-uFF5AuFF66-uFFBEuFFC2-uFFC7uFFCA-uFFCFuFFD2-uFFD7uFFDA-uFFDC][x240-9A-Zx5Fa-zxAAxB5xBAxC0-xD6xD8-xF6xF8-u02C1u02C6-u02D1u02E0-u02E4u02ECu02EEu0300-u0374u0376u0377u037A-u037Du0386u0388-u038Au038Cu038E-u03A1u03A3-u03F5u03F7-u0481u0483-u0487u048A-u0527u0531-u0556u0559u0561-u0587u0591-u05BDu05BFu05C1u05C2u05C4u05C5u05C7u05D0-u05EAu05F0-u05F2u0610-u061Au0620-u0669u066E-u06D3u06D5-u06DCu06DF-u06E8u06EA-u06FCu06FFu0710-u074Au074D-u07B1u07C0-u07F5u07FAu0800-u082Du0840-u085Bu08A0u08A2-u08ACu08E4-u08FEu0900-u0963u0966-u096Fu0971-u0977u0979-u097Fu0981-u0983u0985-u098Cu098Fu0990u0993-u09A8u09AA-u09B0u09B2u09B6-u09B9u09BC-u09C4u09C7u09C8u09CB-u09CEu09D7u09DCu09DDu09DF-u09E3u09E6-u09F1u0A01-u0A03u0A05-u0A0Au0A0Fu0A10u0A13-u0A28u0A2A-u0A30u0A32u0A33u0A35u0A36u0A38u0A39u0A3Cu0A3E-u0A42u0A47u0A48u0A4B-u0A4Du0A51u0A59-u0A5Cu0A5Eu0A66-u0A75u0A81-u0A83u0A85-u0A8Du0A8F-u0A91u0A93-u0AA8u0AAA-u0AB0u0AB2u0AB3u0AB5-u0AB9u0ABC-u0AC5u0AC7-u0AC9u0ACB-u0ACDu0AD0u0AE0-u0AE3u0AE6-u0AEFu0B01-u0B03u0B05-u0B0Cu0B0Fu0B10u0B13-u0B28u0B2A-u0B30u0B32u0B33u0B35-u0B39u0B3C-u0B44u0B47u0B48u0B4B-u0B4Du0B56u0B57u0B5Cu0B5Du0B5F-u0B63u0B66-u0B6Fu0B71u0B82u0B83u0B85-u0B8Au0B8E-u0B90u0B92-u0B95u0B99u0B9Au0B9Cu0B9Eu0B9Fu0BA3u0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