Íèæå ïðèâåäåí êîä ñêðèïòà:

function send(){
var text=document.getElementById('text').value;
var transl=new Array();
    transl['À']='A';     transl['à']='a';
    transl['Á']='B';     transl['á']='b';
    transl['Â']='V';     transl['â']='v';
    transl['Ã']='G';     transl['ã']='g';
    transl['Ä']='D';     transl['ä']='d';
    transl['Å']='E';     transl['å']='e';
    transl['¨']='Yo';    transl['¸']='yo';
    transl['Æ']='Zh';    transl['æ']='zh';
    transl['Ç']='Z';     transl['ç']='z';
    transl['È']='I';     transl['è']='i';
    transl['É']='J';     transl['é']='j';
    transl['Ê']='K';     transl['ê']='k';
    transl['Ë']='L';     transl['ë']='l';
    transl['Ì']='M';     transl['ì']='m';
    transl['Í']='N';     transl['í']='n';
    transl['Î']='O';     transl['î']='o';
    transl['Ï']='P';     transl['ï']='p';
    transl['Ð']='R';     transl['ð']='r';
    transl['Ñ']='S';     transl['ñ']='s';
    transl['Ò']='T';     transl['ò']='t';
    transl['Ó']='U';     transl['ó']='u';
    transl['Ô']='F';     transl['ô']='f';
    transl['Õ']='X';     transl['õ']='x';
    transl['Ö']='C';     transl['ö']='c';
    transl['×']='Ch';    transl['÷']='ch';
    transl['Ø']='Sh';    transl['ø']='sh';
    transl['Ù']='Shh';    transl['ù']='shh';
    transl['Ú']='"';     transl['ú']='"';
    transl['Û']='Y\'';    transl['û']='y\'';
    transl['Ü']='\'';    transl['ü']='\'';
    transl['Ý']='E\'';    transl['ý']='e\'';
    transl['Þ']='Yu';    transl['þ']='yu';
    transl['ß']='Ya';    transl['ÿ']='ya';

    var result='';
    for(i=0;i<text.length;i++) {
        if(transl[text[i]]!=undefined) { result+=transl[text[i]]; }
        else { result+=text[i]; }
    }
    document.getElementById('text').value=result;
}
</script>
<div align="center">
<textarea id="text" cols="35" rows="8" style="width:400px; height:150px;
    color:#0C3A45; border:1px solid #CCCCCC; background:#F2F2F2;"></textarea>
<br>
<input id="send" type="button" value="Ïåðåâåñòè" onclick="send()">
</div>