Javascript 的htmlspecialchars

function htmlspecialchars(ch) {
if (ch===null) return '';
ch = ch.replace(/&/g,"&");
ch = ch.replace(/\"/g,""");
ch = ch.replace(/\'/g,"'");
ch = ch.replace(/</g,"&lt;");
ch = ch.replace(/>/g,"&gt;");
return ch;
}


function unhtmlspecialchars(ch) {
if (ch===null) return '';
ch = ch.replace("&amp;","&");
ch = ch.replace("&quot;","\"");
ch = ch.replace("&#039;","\'");
ch = ch.replace("&lt;","<");
ch = ch.replace("&gt;",">");
return ch;
}