I have a date and a format for that date, given by the user. (d.m.yyyy and 15.10.2021 used for this example)
From that format, I need to get the position of the year, month and day, so that I can use that position on the date.
const year = /y{4}|y{2}/.exec(format);
const month = /m{1,2}/.exec(format);
const day = /d{1,2}/.exec(format);
const yearVal = date.substring(year.index, year.index + year[0].length);
The problem with this is that the format has 1 letter, but my date has 2 numbers. (d and 15.) So i get 0.20 instead of 2021 How can i change this to work with all the different formats?
You can see all the possible formats here: node-dateformat
For example: the difference between "d" and "dd" are like this:
"d" Day of the month as digits; no leading zero for single-digit days.
"dd" Day of the month as digits; leading zero for single-digit days.
You could generate a regex from the pattern like this:
format.replace(/([ymd])\1*/g, (match, ymd) => `(?<${ymd}>${'\\d'.repeat(match.length)})`);
yyyy-mm-dd will become /(<?y>\d\d\d\d)-(<?m>\d\d)-(<?d>\d\d)/, then you can extract the year/month/day using group names:
function getDates(format, date) {
const regex = new RegExp(format.replace(/(\w)\1+|(\w)/g, ({length}, w, s) => `(?<${w||s}>${s ? '\\d+' : '\\d'.repeat(length)})`));
const result = date.match(regex);
if(result) {
const { y: year, m: month, d: day } = result.groups;
return { year, month, day };
}
}
console.log(getDates('yyyy-mm-dd', '2021-10-15'));
console.log(getDates('dd/mm/yyyy', '15/10/2021'));
console.log(getDates('mm-dd-yy', '10-15-21'));
console.log('----');
console.log(getDates('yyyy-m-d', '2021-9-15'));
console.log(getDates('yyyy-m-d', '2021-10-6'));Another option here to split the format & value, lookup y/m/d at respective index
const lookup = ( format, value ) => {
const f = format.split(/(m+|d+|y+)/).filter(Boolean);
const v = value.split(/(\D+)/).filter(Boolean);
return [
v[f.findIndex(i => i.startsWith('y'))],
v[f.findIndex(i => i.startsWith('m'))],
v[f.findIndex(i => i.startsWith('d'))]
];
}
console.log(lookup('d.m.yyyy', '10.5.2021'));
console.log(lookup('d.m.yyyy', '10.12.2021'));
console.log(lookup('dd.mm.yyyy', '10.05.2021'));