在数据添加到DOM时候，我们可以需要对内容进行HtmlEncode或JavaScriptEncode，以预防XSS攻击。
JavaScriptEncode
使用“\”对特殊字符进行转义，除数字字母之外，小于127的字符编码使用16进制“\xHH”的方式进行编码，大于用unicode（非常严格模式）。
//使用“\”对特殊字符进行转义，除数字字母之外，小于127使用16进制“\xHH”的方式进行编码，大于用unicode（非常严格模式）。var JavaScriptEncode = function(str){ var hex=new Array('0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'); function changeTo16Hex(charCode){ return "\\x" + charCode.charCodeAt(0).toString(16); } function encodeCharx(original) { var found = true; var thecharchar = original.charAt(0); var thechar = original.charCodeAt(0); switch(thecharchar) { case '\n': return "\\n"; break; //newline case '\r': return "\\r"; break; //Carriage return case '\'': return "\\'"; break; case '"': return "\\\""; break; case '\&': return "\\&"; break; case '\\': return "\\\\"; break; case '\t': return "\\t"; break; case '\b': return "\\b"; break; case '\f': return "\\f"; break; case '/': return "\\x2F"; break; case '<': return "\\x3C"; break; case '>': return "\\x3E"; break; default: found=false; break; } if(!found){ if(thechar > 47 && thechar < 58){ //数字 return original; } if(thechar > 64 && thechar < 91){ //大写字母 return original; } if(thechar > 96 && thechar < 123){ //小写字母 return original; } if(thechar>127) { //大于127用unicode var c = thechar; var a4 = c%16; c = Math.floor(c/16); var a3 = c%16; c = Math.floor(c/16); var a2 = c%16; c = Math.floor(c/16); var a1 = c%16; return "\\u"+hex[a1]+hex[a2]+hex[a3]+hex[a4]+""; } else { return changeTo16Hex(original); } } } var preescape = str; var escaped = ""; var i=0; for(i=0; i < preescape.length; i++){ escaped = escaped + encodeCharx(preescape.charAt(i)); } return escaped;} HtmlEncode
将字符转换成HTMLEntites，以对抗XSS。
var HtmlEncode = function(str){ var hex = new Array('0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'); var preescape = str; var escaped = ""; for(var i = 0; i < preescape.length; i++){ var p = preescape.charAt(i); escaped = escaped + escapeCharx(p); } return escaped; function escapeCharx(original){ var found=true; var thechar=original.charCodeAt(0); switch(thechar) { case 10: return ""; break; //newline case 32: return " "; break; //space case 34:return """; break; //" case 38:return "&"; break; //& case 39:return "'"; break; //' case 47:return "/"; break; // / case 60:return "<"; break; //< case 62:return ">"; break; //> case 198:return "Æ"; break; case 193:return "Á"; break; case 194:return "Â"; break; case 192:return "À"; break; case 197:return "Å"; break; case 195:return "Ã"; break; case 196:return "Ä"; break; case 199:return "Ç"; break; case 208:return "Ð"; break; case 201:return "É"; break; case 202:return "Ê"; break; case 200:return "È"; break; case 203:return "Ë"; break; case 205:return "Í"; break; case 206:return "Î"; break; case 204:return "Ì"; break; case 207:return "Ï"; break; case 209:return "Ñ"; break; case 211:return "Ó"; break; case 212:return "Ô"; break; case 210:return "Ò"; break; case 216:return "Ø"; break; case 213:return "Õ"; break; case 214:return "Ö"; break; case 222:return "Þ"; break; case 218:return "Ú"; break; case 219:return "Û"; break; case 217:return "Ù"; break; case 220:return "Ü"; break; case 221:return "Ý"; break; case 225:return "á"; break; case 226:return "â"; break; case 230:return "æ"; break; case 224:return "à"; break; case 229:return "å"; break; case 227:return "ã"; break; case 228:return "ä"; break; case 231:return "ç"; break; case 233:return "é"; break; case 234:return "ê"; break; case 232:return "è"; break; case 240:return "ð"; break; case 235:return "ë"; break; case 237:return "í"; break; case 238:return "î"; break; case 236:return "ì"; break; case 239:return "ï"; break; case 241:return "ñ"; break; case 243:return "ó"; break; case 244:return "ô"; break; case 242:return "ò"; break; case 248:return "ø"; break; case 245:return "õ"; break; case 246:return "ö"; break; case 223:return "ß"; break; case 254:return "þ"; break; case 250:return "ú"; break; case 251:return "û"; break; case 249:return "ù"; break; case 252:return "ü"; break; case 253:return "ý"; break; case 255:return "ÿ"; break; case 162:return "¢"; break; case '\r': break; default: found=false; break; } if(!found){ if(thechar>127) { var c=thechar; var a4=c%16; c=Math.floor(c/16); var a3=c%16; c=Math.floor(c/16); var a2=c%16; c=Math.floor(c/16); var a1=c%16; return "&#x"+hex[a1]+hex[a2]+hex[a3]+hex[a4]+";"; } else{ return original; } } }} Test
<script>alert('1哈哈' /);</script>
这些编码后的内容都能在页面上显示正常。
番外
还有人弄了简单HtmlEncode，有两种方式。
1. 用浏览器内部转换器实现html转码（但我觉得这种方式有风险的，因为内部转换器可能有漏洞）。
2. 只转一部分html字符（这种方式不完整）。
var HtmlUtil = { htmlEncode:function (html){ var temp = document.createElement ("div"); (temp.textContent != undefined ) ? (temp.textContent = html) : (temp.innerText = html); var output = temp.innerHTML; temp = null; return output; }, htmlDecode:function (text){ var temp = document.createElement("div"); temp.innerHTML = text; var output = temp.innerText || temp.textContent; temp = null; return output; }, htmlEncodeByRegExp:function (str){ var s = ""; if(str.length == 0) return ""; s = str.replace(/&/g,"&"); s = s.replace(//g,">"); s = s.replace(/ /g," "); s = s.replace(/\'/g,"'"); s = s.replace(/\"/g,"""); return s; }, htmlDecodeByRegExp:function (str){ var s = ""; if(str.length == 0) return ""; s = str.replace(/&/g,"&"); s = s.replace(/</g,"<"); s = s.replace(/>/g,">"); s = s.replace(/ /g," "); s = s.replace(/'/g,"\'"); s = s.replace(/"/g,"\""); return s; }};
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