html mysql special character

function html_encode(str)
{
  var s = "";
  if (str.length == 0) return "";
  s = str.replace(/&/g, "&");
  s = s.replace(/</g, "&lt;");
  s = s.replace(/>/g, "&gt;");
  //s = s.replace(/ /g, "&nbsp;");
  s = s.replace(/\‘/g, "'");
  s = s.replace(/\"/g, "&quot;");
  //s = s.replace(/\n/g, "<br>");
  return s;
}   

function html_decode(str)
{
  var s = "";
  if (str.length == 0) return "";
  s = str.replace(/&amp;/g, "&");
  s = s.replace(/&lt;/g, "<");
  s = s.replace(/&gt;/g, ">");
  s = s.replace(/&nbsp;/g, " ");
  s = s.replace(/'/g, "\‘");
  s = s.replace(/&quot;/g, "\"");
  s = s.replace(/<br>/g, "\n");
  return s;
}