Two methods for JavaScript to determine whether the entered date is a legal date

JavaScript code
/// Check whether the entered date is a correct date format:
/// Supports four input formats: yyyy-M-d, yyyy-MM-dd, yyyy/M/d, yyyy/MM/dd.

function checkDate(strInputDate) {
// Define a constant array of days in a month
var DA = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

// Unified date format
strDate = strInputDate.replace(/-/g, "/");

// Determine whether the date is in the expected format
if (strDate.indexOf("/") == -1) {
alert("Please enter the format of yyyy-M-d, yyyy-MM-dd, yyyy/M/d, yyyy/MM/dd.")
return false;
}

// Decompose the year, month and day
arrD = strDate.split("/");
if (arrD.length != 3) return false;
y = parseInt(arrD[0], 10);
m = parseInt(arrD[1], 10);
d = parseInt(arrD[2], 10);

//Judge whether the year, month and day are numbers
if (isNaN(y) || isNaN(m) || isNaN(d)) return false;

//Judge Whether the month is between 1-12
if (m > 12 || m < 1) return false;
//Determine whether it is a leap year
if (isLoopYear(y)) DA[2] = 29;

/ /Determine whether the entered day exceeds the total number of days in the current month.
if (d > DA[m]) return false;

//If all conditions are verified, it should be a legal date.
// If you want to format the date once, you can do it here. The following formats it into the date format recognized by the database yyyy-MM-dd
// str = y + "-" + (m<10?" 0":"") + m + "-" + (d<10?"0":"") + d;
str = y + "-" + (m < 10 ? "0" : "") + m + "-" + (d < 10 ? "0" : "") + d;
alert(str)
return true;
}
function isLoopYear(theYear) {
return (new Date(theYear, 1 , 29).getDate() == 29);
}

//Method 2:
/// Check whether the entered date is a correct date format:
/// Supports yyyy-M-d, yyyy-MM- There are four input formats: dd, yyyy/M/d, yyyy/MM/dd.
function CheckDate2(strInputDate) {
if (strInputDate == "") return false;
strInputDate = strInputDate.replace(/-/g, "/");
var d = new Date(strInputDate);
if (isNaN (d)) return false;
var arr = strInputDate.split("/");
return ((parseInt(arr[0], 10) == d.getFullYear()) && (parseInt(arr[1], 10) == (d.getMonth() + 1)) && (parseInt(arr[2], 10) == d.getDate()));
}