I have the following regex that uses look-behind to match different time formats inside a string:
(?:(?<=[\s])|^)(2[0-3]|[01]?[0-9]):([0-5]?[0-9])(?::([0-5]?[0-9]))?( ?[AP]M)?(?:(?=[\s])|$)
The regex must match 12-hour or 24-hour time formats, with minutes and optional seconds. Examples:
10:00 AM
Time: 10:00 (only the `10:00` part)
13:23:34
The regex should entirely reject the following strings:
hello10:00 (the time is not separated by whitespace)
24:00:00 (24 does not make sense)
9912:1299 (there's a time substring, but the whole string is not really a time).
I'm trying to rewrite it to not use positive look-behind, which is not supported by every web browser. How could I do it?
CodePudding user response：
const rgx = /\b(?:1?\d|2[0-3]):[0-5]\d(?::[0-5]\d)? ?(?:[ap]m)?\b/gi;
| Segment | Description |
|---|---|
\b |
to the left is a non-word and to the right is a word |
(?:1?\d |
begin non-capturing group 0 to 19 |
| |
OR |
2[0-3]) |
20 to 23 end non-capturing group |
:[0-5]\d |
: 00 to 59 |
(?::[0-5]\d)? ? |
same as above with a space or nothing |
(?:[ap]m)? |
a or p then m or nothing |
\b |
to the right is a non-word and to the left is a word |
const rgx = /\b(?:1?\d|2[0-3]):[0-5]\d(?::[0-5]\d)? ?(?:[ap]m)?\b/gi
const str = `
10:00 AM
Time: 10:00
13:23:34
hello10:00
24:00:00
9912:1299`;
const res = [...str.matchAll(rgx)].flat();
console.log(res);CodePudding user response：
Your pattern can be modified to:
(?:^|[ \t])(2[0-3]|[01]?[0-9]):([0-5]?[0-9])(?::([0-5]?[0-9]))?( ?[AP]M)?(?:(?=[\s])|$)