"Javascript's array.splice() function is terrible"? Really? I was quite happy, finding out it can do exactly what I was looking for :-) Thumbs up for the comments!

Great!

awesome solution

Yes there are, but they are already compressed. Note the "::" in the inputs.

B090:2985:9000::6F39:00 -> expected 'b090:2985:9000::6f39:0'

A01C:BA::140C:D:0640:002D -> expected 'a01c:ba::140c:d:640:2d'

There aren't two consecutive groups of just 0 in either of these inputs, why are they valid?

WHen you have more than 2 consecutive groups of just 0, e.g. 1:0:0:0:1 -> 1::1.

I have read the instructions multiple times and I still don't know when it's valid to have fewer than 8 groups.

Essentially a duplicate: https://www.codewars.com/kata/5980d4e258a9f5891e000062 and no Random tests.

Look for "regular expressions".

Hi,

could anyone direct me to the documentation where I can find details like the "(WUB)+" in this code.
I'm not sure if I explain clearly what I'm looking for.
I am looking for the predefined symbols that do operations inside quots "" and are not actually part of the String.

Thanks in advance.

input:              1:1:0:0:1::1
"conracted" from:   1:1:0:0:1:0:0:1
valid contraction:  1:1::1:0:0:1

The rule that the first longest group must be contracted is ignored here, hence this input should be considered as invalid, and yet the tests consider it to be correct. Either this case should be removed or it should be changed to expect false.

random tests?

Very good Kata!
...
Nice job, mr.MindWanderer!

Excellent kata :)