/* code from qodo.co.uk */
// create as many regular expressions here as you need:
var digitsOnly = /[0-9]/g;
var floatOnly = /[0-9\.]/g;
var alphaOnly = /[A-Za-z]/g;
function restrictCharacters(field, e, restrictionType) {
    if (!e) {
        var e = window.event;
    }

    if (e.keyCode) {
        code = e.keyCode;
    } else if (e.which) {
        code = e.which;
    }

    var character = String.fromCharCode(code);

    // if they pressed esc remove focus from field
    if (code==27) { 
        this.blur(); return false; 
    }
    // ignore if they press other keys
    // strange because code: 39 is the down key AND ' key...
    // and DEL also equals .
    if (!e.ctrlKey && code!=9 && code!=8 && code!=36 && code!=37 && code!=38 && (code!=39 || (code==39 && character=="'")) && code!=40) {
        if (character.match(restrictionType)) {
            return true;
        } else {
            return false;
        }
    }
}

// Use with onkeyup.
var _restrict_prev_value = '';
function restrictFormat(field, format) {
    if (field.value.match(format)) {
        _restrict_prev_value = field.value;
        return true;
    } else {
        field.value = _restrict_prev_value;
        return false;
    }
}