RegEx - LIFO buffer on match events

Question

How is it possible to make a LIFO buffer on match events by using regex in Javascript?
Here's an example:

Input:

4   Mål Vålerenga, 1 - 0 Torgeir Børven. Målgivende pasning Daniel Fredheim Holm.<br> Dagens kaptein, Fredheim Holm, med en smart stikker til Børven, som drar seg fri og tupper ballen vakkert i lengste hjørne. Vålerenga innleder jubileet med 1-0!<br>
3    Fellah spilles fri på høyreflanken, men assistentdommeren vinker som om det skulle være 100-årsjubileum og 17. mai på en gang. Offside.
2   Corner Sarpsborg 08, Gudmundur Thórarinsson. Klareres.<br>
1    Kampen starter med forbrødring mellom keeperne. Kongshavn banker ballen helt over til kollega Sukke.<br>

Output should be:

1    Kampen starter med forbrødring mellom keeperne. Kongshavn banker ballen helt over til kollega Sukke.<br>
2   Corner Sarpsborg 08, Gudmundur Thórarinsson. Klareres.<br>
3    Fellah spilles fri på høyreflanken, men assistentdommeren vinker som om det skulle være 100-årsjubileum og 17. mai på en gang. Offside.<br>
4   Mål Vålerenga, 1 - 0 Torgeir Børven. Målgivende pasning Daniel Fredheim Holm.<br>

What are you matching with the regular expression? What regular expression are you using? It looks to me like you're just reversing the order of the lines, which doesn't require a regular expression at all. — Barmar, Aug 03 '13 at 06:51
Yes i will just reverse the order of the lines. But I should use regex to identify where to reverse. Fx regex should match if the string contains 1,2,3,4,5,6,7,...90 — Cemil Akbulut, Aug 03 '13 at 06:55
The input is one long string, so the system has to identify 1,2,3,4,5,...,90 — Cemil Akbulut, Aug 03 '13 at 06:56
@CemilAkbulut How do you do it? is it array or what? if array you can sort it using .sort() right? — Praveen, Aug 03 '13 at 06:57
if this is homework or quiz you should say it, but if it's not, there is more suitable method than regex to do this shorting — Angga, Aug 03 '13 at 07:13

score 0 · Answer 1 · answered Aug 03 '13 at 10:41

It's not possible with regex alone (at least in JavaScript's regex flavor), but you can use regex matching or splitting and reverse:

If your input is as simple as in the question, then instead of matching you can split. We simply split the string at the beginning of each line:

result = str.split(/^/m).reverse().join("");

In more complex situations, splitting might not be that easy and you actually need to match. Still using your example, you could match the lines with .*\n (since . cannot match line breaks). In that case you can use

result = str.match(/.*\n/g).reverse().join("");

The problem here is to ensure that your matches will cover the entire input string - otherwise characters are lost in the process (this cannot happen with the split approach - but some problems will be to difficult to tackle with a JavaScript regex in split).

RegEx - LIFO buffer on match events

1 Answers1