Javascript: encode(decode) html text into html entity

comeonman.js

// encode(decode) html text into html entity
function decodeHtmlEntity(str) {
  return str.replace(/&#(\d+);/g, function(match, dec) {
    return String.fromCharCode(dec);
  });
};

function encodeHtmlEntity(str) {
  var buf = '';
  for (var i = 0; i < str.length; i++) {
    buf += '&#'+ str.charCodeAt(i) + ';';
  }
  return buf;
};

var entity = '&#20182;&#22920;&#30340;&#19996;&#35199;&#21560;';
var str = '他妈的东西吸';
console.log(decodeHtmlEntity(entity) === str);
console.log(encodeHtmlEntity(str) === entity);
// output:
// true
// true
// undefined