const regex = /(?(DEFINE)
(?# Date )
(?# Day ranges )
(?<d_day28>0[1-9]|1\d|2[0-8]|[1-9])
(?<d_day29>0[1-9]|1\d|2\d|[1-9])
(?<d_day30>0[1-9]|1\d|2\d|30|[1-9])
(?<d_day31>0[1-9]|1\d|2\d|3[01]|[1-9])
(?# Month specifications )
(?<d_month28>0?2)
(?<d_month29>0?2)
(?<d_month30>0?[469]|11)
(?<d_month31>0?[13578]|1[02])
(?# Year specifications )
(?<d_year>\d+)
(?<d_yearLeap>(?:\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\D|\b))
(?# Valid date formats )
(?<d_format>
(?&d_day28)-(?&d_month28)-(?&d_year)|
(?&d_day29)-(?&d_month29)-(?&d_yearLeap)|
(?&d_day30)-(?&d_month30)-(?&d_year)|
(?&d_day31)-(?&d_month31)-(?&d_year)
)
)
\b(?&d_format)\b/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?(DEFINE)
(?# Date )
(?# Day ranges )
(?<d_day28>0[1-9]|1\\d|2[0-8]|[1-9])
(?<d_day29>0[1-9]|1\\d|2\\d|[1-9])
(?<d_day30>0[1-9]|1\\d|2\\d|30|[1-9])
(?<d_day31>0[1-9]|1\\d|2\\d|3[01]|[1-9])
(?# Month specifications )
(?<d_month28>0?2)
(?<d_month29>0?2)
(?<d_month30>0?[469]|11)
(?<d_month31>0?[13578]|1[02])
(?# Year specifications )
(?<d_year>\\d+)
(?<d_yearLeap>(?:\\d*?(?:(?:0[48]|[13579][26]|[2468][048])|(?:(?:[02468][048]|[13579][26])00))|[48]00|[48])(?=\\D|\\b))
(?# Valid date formats )
(?<d_format>
(?&d_day28)-(?&d_month28)-(?&d_year)|
(?&d_day29)-(?&d_month29)-(?&d_yearLeap)|
(?&d_day30)-(?&d_month30)-(?&d_year)|
(?&d_day31)-(?&d_month31)-(?&d_year)
)
)
\\b(?&d_format)\\b', 'gm')
const str = `29-02-2016 - valid
29-02-2017 - invalid (not leap year)
30-03-2016 - valid
29-2-2017 - invalid (not leap year)
28-2-2017 - valid
2-2-2017 - valid
31-11-2017 - invalid (November has 30 days)
30-11-2017 - valid`;
// Reset `lastIndex` if this regex is defined globally
// regex.lastIndex = 0;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions