How to parse a time into a Date object from user input in JavaScript?

Solution 1:

A quick solution which works on the input that you've specified:

function parseTime( t ) {
   var d = new Date();
   var time = t.match( /(\d+)(?::(\d\d))?\s*(p?)/ );
   d.setHours( parseInt( time[1]) + (time[3] ? 12 : 0) );
   d.setMinutes( parseInt( time[2]) || 0 );
   return d;
}

var tests = [
  '1:00 pm','1:00 p.m.','1:00 p','1:00pm','1:00p.m.','1:00p','1 pm',
  '1 p.m.','1 p','1pm','1p.m.', '1p', '13:00','13', '1a', '12', '12a', '12p', '12am', '12pm', '2400am', '2400pm', '2400', 
  '1000', '100', '123', '2459', '2359', '2359am', '1100', '123p',
  '1234', '1', '9', '99', '999', '9999', '99999', '0000', '0011', '-1', 'mioaw' ];

for ( var i = 0; i < tests.length; i++ ) {
  console.log( tests[i].padStart( 9, ' ' ) + " = " + parseTime(tests[i]) );
}

It should work for a few other varieties as well (even if a.m. is used, it'll still work - for example). Obviously this is pretty crude but it's also pretty lightweight (much cheaper to use that than a full library, for example).

Warning: The code doe not work with 12:00 AM, etc.

Solution 2:

All of the examples provided fail to work for times from 12:00 am to 12:59 am. They also throw an error if the regex does not match a time. The following handles this:

function parseTime(timeString) {	
	if (timeString == '') return null;
	
	var time = timeString.match(/(\d+)(:(\d\d))?\s*(p?)/i);	
	if (time == null) return null;
	
	var hours = parseInt(time[1],10);	 
	if (hours == 12 && !time[4]) {
		  hours = 0;
	}
	else {
		hours += (hours < 12 && time[4])? 12 : 0;
	}	
	var d = new Date();    	    	
	d.setHours(hours);
	d.setMinutes(parseInt(time[3],10) || 0);
	d.setSeconds(0, 0);	 
	return d;
}


var tests = [
  '1:00 pm','1:00 p.m.','1:00 p','1:00pm','1:00p.m.','1:00p','1 pm',
  '1 p.m.','1 p','1pm','1p.m.', '1p', '13:00','13', '1a', '12', '12a', '12p', '12am', '12pm', '2400am', '2400pm', '2400', 
  '1000', '100', '123', '2459', '2359', '2359am', '1100', '123p',
  '1234', '1', '9', '99', '999', '9999', '99999', '0000', '0011', '-1', 'mioaw' ];

for ( var i = 0; i < tests.length; i++ ) {
  console.log( tests[i].padStart( 9, ' ' ) + " = " + parseTime(tests[i]) );
}

This will work for strings which contain a time anywhere inside them. So "abcde12:00pmdef" would be parsed and return 12 pm. If the desired outcome is that it only returns a time when the string only contains a time in them the following regular expression can be used provided you replace "time[4]" with "time[6]".

/^(\d+)(:(\d\d))?\s*((a|(p))m?)?$/i

How to parse a time into a Date object from user input in JavaScript?

Solution 1:

Solution 2:

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