Thank You @Jonathan. I found the solution in your link.
This function do exact what I want:
function encodeHTML(str) {
var aStr = str.split(''),
i = aStr.length,
aRet = [];
while (--i) {
var iC = aStr[i].charCodeAt();
if (iC < 65 || iC > 127 || (iC > 90 && iC < 97)) {
aRet.push('&#' + iC + ';');
} else {
aRet.push(aStr[i]);
}
}
return aRet.reverse().join('');
}