htmlentity.js

// encode(decode) html text into html entity (assuming entity is hex)
var HtmlEntity = {
  decode : function(str) {
    return str.replace(/&#x([0-9A-F]+);/gi, function(match, dec) {
      return String.fromCharCode(parseInt(dec, 16));
    });
  },

  encode : function(str) {
    var buf = [];
    for (var i = 0, length = str.length; i < length; i++) {
      buf.push("&#x" + str[i].charCodeAt().toString(16) + ";");
    }
    return buf.join("");
  }
};

var entity = '&#x9ad8;&#x7ea7;&#x7a0b;&#x5e8f;&#x8bbe;&#x8ba1;';
var str = '高级程序设计';
console.log(HtmlEntity.decode(entity) === str); // true
console.log(HtmlEntity.encode(str) === entity); // true