javascript检查字符串是否为有效的日期

/*----------------*/



/**

* DHTML date validation script. Courtesy of SmartWebby.com (http://www.smartwebby.com/dhtml/)

*/

// Declaring valid date character, minimum year and maximum year

var dtCh= "/";

var minYear=1900;

var maxYear=2100;



function isInteger(s){

   var i;

    for (i = 0; i < s.length; i++){   

       // Check that current character is number.

       var c = s.charAt(i);

       if (((c < "0") || (c > "9"))) return false;

    }

    // All characters are numbers.

    return true;

}



function stripCharsInBag(s, bag){

   var i;

    var returnString = "";

    // Search through string's characters one by one.

    // If character is not in bag, append to returnString.

    for (i = 0; i < s.length; i++){   

       var c = s.charAt(i);

       if (bag.indexOf(c) == -1) returnString += c;

    }

    return returnString;

}



function daysInFebruary (year){

   // February has 29 days in any year evenly divisible by four,

    // EXCEPT for centurial years which are not also divisible by 400.

    return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );

}

function DaysArray(n) {

   for (var i = 1; i <= n; i++) {

       this[i] = 31

       if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}

       if (i==2) {this[i] = 29}

  }

  return this

}



function isDate(dtStr){

   var daysInMonth = DaysArray(12)

   var pos1=dtStr.indexOf(dtCh)

   var pos2=dtStr.indexOf(dtCh,pos1+1)

   var strMonth=dtStr.substring(0,pos1)

   var strDay=dtStr.substring(pos1+1,pos2)

   var strYear=dtStr.substring(pos2+1)

   strYr=strYear

   if (strDay.charAt(0)=="0" && strDay.length>1) strDay=strDay.substring(1)

   if (strMonth.charAt(0)=="0" && strMonth.length>1) strMonth=strMonth.substring(1)

   for (var i = 1; i <= 3; i++) {

       if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1)

   }

   month=parseInt(strMonth)

   day=parseInt(strDay)

   year=parseInt(strYr)

   if (pos1==-1 || pos2==-1){

       alert("The date format should be : mm/dd/yyyy")

       return false

   }

   if (strMonth.length<1 || month<1 || month>12){

       alert("Please enter a valid month")

       return false

   }

   if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month]){

       alert("Please enter a valid day")

       return false

   }

   if (strYear.length != 4 || year==0 || year<minYear || year>maxYear){

       alert("Please enter a valid 4 digit year between "+minYear+" and "+maxYear)

       return false

   }

   if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false){

       alert("Please enter a valid date")

       return false

   }

return true

}