需要帮助，以确认是否使用JavaScript是过去的日期

Question

Hi I am currently stuck on how to carve up my regex date to then test if the date entered is in the past . if it is I would like to alert this.

I know i some how need to splice my regex but im unsure how to do this any help would be much appreciated. below is my script so far its a pretty long regex but it covers everything including leap years but like i said i know need to break it down by either substr or splice.

//start of datefield
var dateformat=/^(?:(?:31\/(?:0[13578]|1[02])|(?:29|30)\/(?:0[13-9]|1[012])|(?:0[1-9]|1\d|2[0-8])\/(?:0[1-9]|1[0-2]))\/[2-9]\d{3}|29\/02\/(?:[2-9]\d(?:0[48]|[2468][048]|[13579][26])|(?:[2468][048]|[3579][26])00))$/;

if (!date.match(dateformat))
{
    alert("format incorrect use dd/mm/yyyy make sure you are entering correct days to the month remember 30 days have september, april, june & november, only 28 days in february unless leap year next is 2016");
    return false;
}
//end date field

Answer 1

Simple

date = "12/11/2009";
if(new Date(date) < new Date()){
     // a
} else {
     // b
}

Answer 2

Using a regular expression to work out if a date is valid or is before or after some other time is not the easiest way to do the job. Much easier to turn the string into a date object and test that.

So parse the string to create a date object and go from there. You shouldn't leave parsing of date strings to the date object as it is mostly implementation dependent (ECMA-262 specifies a version of ISO8601 but it is not supported by all browsers in use). So if your format is d/m/y you can do:

function isDateHistory(s) {
  s = s.split('/');
  return (new Date(s[2], --s[1], s[0])) < (new Date());
}

alert(isDateHistory('15/6/2013')); // true
alert(isDateHistory('15/7/2013')); // false

You can also validate the date using:

function validateDate(dateString) {
  var s = dateString.split('/');
  var d = new Date(s[2], --s[1], s[0]);
  return d && d.getFullYear() == s[2] && d.getDate() == s[0];
}