function is_array( mixed_var ) {
    return ( mixed_var instanceof Array );
}
function str_replace(search, replace, subject) {
    var f = search, r = replace, s = subject;
    var ra = is_array(r), sa = is_array(s), f = [].concat(f), r = [].concat(r), i = (s = [].concat(s)).length;
 
    while (j = 0, i--) {
        while (s[i] = s[i].split(f[j]).join(ra ? r[j] || "" : r[0]), ++j in f){};
    };
     
    return sa ? s : s[0];
}