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    某比赛实在有点坑人，题目涉嫌抄袭不说，还不停改来改去。算了不吐槽了，说一则javascript小特性吧。

    toUpperCase()是javascript中将小写转换成大写的函数。toLowerCase()是javascript中将大写转换成小写的函数。但是这俩函数真的只有这两个功能么？

    不如我们来fuzz一下，看看toUpperCase功能如何？

brush: js;auto-links: false;">if (!String.fromCodePoint) {(function() {var defineProperty = (function() {// IE 8 only supports `Object.defineProperty` on DOM elementstry {var object = {};var $defineProperty = Object.defineProperty;var result = $defineProperty(object, object, object) && $defineProperty;} catch(error) {}return result;}());var stringFromCharCode = String.fromCharCode;var floor = Math.floor;var fromCodePoint = function() {var MAX_SIZE = 0x4000;var codeUnits = [];var highSurrogate;var lowSurrogate;var index = -1;var length = arguments.length;if (!length) {return '';}var result = '';while (++index < length) {var codePoint = Number(arguments[index]);if (!isFinite(codePoint) || // `NaN`, `+Infinity`, or `-Infinity`codePoint < 0 || // not a valid Unicode code pointcodePoint > 0x10FFFF || // not a valid Unicode code pointfloor(codePoint) != codePoint // not an integer) {throw RangeError('Invalid code point: ' + codePoint);}if (codePoint <= 0xFFFF) { // BMP code pointcodeUnits.push(codePoint);} else { // Astral code point; split in surrogate halves// http://mathiasbynens.be/notes/javascript-encoding#surrogate-formulaecodePoint -= 0x10000;highSurrogate = (codePoint >> 10) + 0xD800;lowSurrogate = (codePoint % 0x400) + 0xDC00;codeUnits.push(highSurrogate, lowSurrogate);}if (index + 1 == length || codeUnits.length > MAX_SIZE) {result += stringFromCharCode.apply(null, codeUnits);codeUnits.length = 0;}}return result;};if (defineProperty) {defineProperty(String, 'fromCodePoint', {'value': fromCodePoint,'configurable': true,'writable': true});} else {String.fromCodePoint = fromCodePoint;}}());}for (var j = 'A'.charCodeAt(); j <= 'Z'.charCodeAt(); j++){var s = String.fromCodePoint(j);for (var i = 0; i < 0x10FFFF; i++) {var e = String.fromCodePoint(i);if (s == e.toUpperCase() && s != e) {document.write("char: "+e+"<br/>");};};}

    结果我们可以看到：

    

    其中混入了两个奇特的字符"ı"、"ſ"。

    这两个字符的“大写”是I和S。也就是说"ı".toUpperCase() == 'I'，"ſ".toUpperCase() == 'S'。通过这个小特性可以绕过一些限制。

    同样，toLowerCase也有同样的字符：

    

    这个"K"的“小写”字符是k，也就是"K".toLowerCase() == 'k'.

    用这个特性可以完成 http://prompt.ml/9 。还有某比赛的神题，当然有更简单的方法。