//<,>转化成转义字符

function html_encode(str)

{

  var s = "";

  if (str.length == 0) return "";

  s = str.replace(/&/g, "&gt;");

  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;

}

//转义字符反转义为标签符

function html_decode(str)

{

  var s = "";

  if (str.length == 0) return "";

  s = str.replace(/>/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;

}