How to parse a time into a Date object from user input in JavaScript?
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.
Most of the regex solutions here throw errors when the string can't be parsed, and not many of them account for strings like 1330 or 130pm. Even though these formats weren't specified by the OP, I find them critical for parsing dates input by humans.
All of this got me to thinking that using a regular expression might not be the best approach for this.
My solution is a function that not only parses the time, but also allows you to specify an output format and a step (interval) at which to round minutes to. At about 70 lines, it's still lightweight and parses all of the aforementioned formats as well as ones without colons.
- Demo: http://jsfiddle.net/HwwzS/1/
- Code: https://gist.github.com/claviska/4744736
function parseTime(time, format, step) {
var hour, minute, stepMinute,
defaultFormat = 'g:ia',
pm = time.match(/p/i) !== null,
num = time.replace(/[^0-9]/g, '');
// Parse for hour and minute
switch(num.length) {
case 4:
hour = parseInt(num[0] + num[1], 10);
minute = parseInt(num[2] + num[3], 10);
break;
case 3:
hour = parseInt(num[0], 10);
minute = parseInt(num[1] + num[2], 10);
break;
case 2:
case 1:
hour = parseInt(num[0] + (num[1] || ''), 10);
minute = 0;
break;
default:
return '';
}
// Make sure hour is in 24 hour format
if( pm === true && hour > 0 && hour < 12 ) hour += 12;
// Force pm for hours between 13:00 and 23:00
if( hour >= 13 && hour <= 23 ) pm = true;
// Handle step
if( step ) {
// Step to the nearest hour requires 60, not 0
if( step === 0 ) step = 60;
// Round to nearest step
stepMinute = (Math.round(minute / step) * step) % 60;
// Do we need to round the hour up?
if( stepMinute === 0 && minute >= 30 ) {
hour++;
// Do we need to switch am/pm?
if( hour === 12 || hour === 24 ) pm = !pm;
}
minute = stepMinute;
}
// Keep within range
if( hour <= 0 || hour >= 24 ) hour = 0;
if( minute < 0 || minute > 59 ) minute = 0;
// Format output
return (format || defaultFormat)
// 12 hour without leading 0
.replace(/g/g, hour === 0 ? '12' : 'g')
.replace(/g/g, hour > 12 ? hour - 12 : hour)
// 24 hour without leading 0
.replace(/G/g, hour)
// 12 hour with leading 0
.replace(/h/g, hour.toString().length > 1 ? (hour > 12 ? hour - 12 : hour) : '0' + (hour > 12 ? hour - 12 : hour))
// 24 hour with leading 0
.replace(/H/g, hour.toString().length > 1 ? hour : '0' + hour)
// minutes with leading zero
.replace(/i/g, minute.toString().length > 1 ? minute : '0' + minute)
// simulate seconds
.replace(/s/g, '00')
// lowercase am/pm
.replace(/a/g, pm ? 'pm' : 'am')
// lowercase am/pm
.replace(/A/g, pm ? 'PM' : 'AM');
}
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]) );
}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
Don't bother doing it yourself, just use datejs.