Javascript function: validate date (yyyy-mm-dd) format via JavaScript.

isValidDate - javascript

/**
 * isValidDate(str)
 * @param string str value yyyy-mm-dd
 * @return boolean true or false
 * IF date is valid return true
 */
function isValidDate(str){
	// STRING FORMAT yyyy-mm-dd
	if(str=="" || str==null){return false;}								
	
	// m[1] is year 'YYYY' * m[2] is month 'MM' * m[3] is day 'DD'					
	var m = str.match(/(\d{4})-(\d{2})-(\d{2})/);
	
	// STR IS NOT FIT m IS NOT OBJECT
	if( m === null || typeof m !== 'object'){return false;}				
	
	// CHECK m TYPE
	if (typeof m !== 'object' && m !== null && m.size!==3){return false;}
				
	var ret = true; //RETURN VALUE						
	var thisYear = new Date().getFullYear(); //YEAR NOW
	var minYear = 1999; //MIN YEAR
	
	// YEAR CHECK
	if( (m[1].length < 4) || m[1] < minYear || m[1] > thisYear){ret = false;}
	// MONTH CHECK			
	if( (m[2].length < 2) || m[2] < 1 || m[2] > 12){ret = false;}
	// DAY CHECK
	if( (m[3].length < 2) || m[3] < 1 || m[3] > 31){ret = false;}
	
	return ret;			
}

Why is a future year an invalid date? (m[1] > thisYear) ? If, for example you want to make an event for january 2015 and it's currently december 2014, this would be flagged as invalid. Perhaps this was for a specific case but in general, any future year should be a valid date.

@michaelsidler Thanks Michael (it looks was copy paste :))!
@afdil13 returned param ret is true or false and that's enough.
@percy3d it is a specific validation and there this parameter can't be higher then this year.

Modified little bit to give a more valid date

// DAY CHECK
if( (m[3].length < 2) || m[3] < 1 || ((["04","06","09","11"].indexOf(m[2]) > -1 && m[3] > 30 ) || m[3] > 31)){ret = false;}
// FEBRUARY CHECK
if( (m[2] == 2 && m[3] > 29) || (m[2] == 2 && m[3] > 28 && m[1]%4 != 0)){ret = false;}

It returned true even for 2017-02-31.
Corrected it

also add stop regex
var m = str.match(/(\d{4})-(\d{2})-(\d{2})$/);

because 2019-02-282 return true

also add stop regex
var m = str.match(/(\d{4})-(\d{2})-(\d{2})$/);

because 2019-02-282 return true

if we just want to check the format, this is the correct way to do it. i can use it in my vuelidate custom checker