用js做日期check

var mstrSaveFieldValue;
            function SaveFieldValue(pobjObject) {
                mstrSaveFieldValue = pobjObject.value;
            }
            function CheckInputText(obj)
            {
                var nowyear = new Date;
                var str = EmpTrim(obj.value);
                obj.value = str;
                if (str == '') return;
                var y, m, d;
                var new_y, new_m, new_d;
                if (str.match(/^(([0-9]{4})\/|)([0-9]{1,2})\/([0-9]{1,2})$/)){
                    y = RegExp.$2;
                    m = RegExp.$3;
                    d = RegExp.$4;
                    if (y == ''){
                        y = nowyear.getFullYear();
                    }
                    if (IsDate(y, RegExp.$3, RegExp.$4)){
                        new_y = ('0000' + y); new_y = new_y.substring(new_y.length-4);
                        new_m = ('00' + m);   new_m = new_m.substring(new_m.length-2);
                        new_d = ('00' + d);   new_d = new_d.substring(new_d.length-2);
                        obj.value = new_y + '/' + new_m + '/' + new_d;
                        return;
                    }
                    else
                    {
                        obj.value = mstrSaveFieldValue;
                    }
                }
                else
                {
                    obj.value = mstrSaveFieldValue;
                }
            }
            function EmpTrim(pstrVal) {
                pstrVal = pstrVal.replace(/^[ 　]+/, '');
                pstrVal = pstrVal.replace(/[ 　]+$/, '');
                return(pstrVal);
            }
            function IsDate(y,m,d){
                var wblnTemp = false;
                var mday = new Array (31,28,31,30,31,30,31,31,30,31,30,31);
                if ((y % 100 == 0) && (y % 400 != 0)) {
                    wblnTemp = false;
                } else if (y % 4 == 0){
                    wblnTemp = true;
                }
                if (wblnTemp) mday[1] = 29;
                if ((y < 1) || (y > 9999)) return false;
                if ((m < 1) || (m > 12)) return false;
                if ((d < 1) || (d > mday[m-1])) return false;
                return true;
            }






<input type="text" wicket:id="createDateFrom" id="createDateFrom" onfocus="SaveFieldValue(this)"　onblur="CheckInputText(this)"　value="2012/07/20" maxlength="10" style="width:85px;vertical-align:middle;" />