Kata

First, You will write a very basic compression algorithm

It gets a string:
string="aaaaaaaabaaaa"
And generates an array that sums all the repeating characters like so:
compressed=[[8,"a"],[1,"b"],[4,"a"]]
The compressed version is turned into a string:
compressed='[[8,"a"],[1,"b"],[4,"a"]]'

Finally,
If the compressed version is shorter than the original string, the function will return the compressed version.
Otherwise it will return the original string.

Example1:
string1="aaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaa"
output1='[[26,"a"],[1,"b"],[18,"a"]]'

Example2:
string2="abcde"
output2="abcde"

After you created the compression algorithm, create a decompression algorithm:

It gets a string (output1, output2, etc.).
If the string is comrpessed, it returns the uncompressed version,
If it is uncompressed, it returns the original string unchanged.

//output1='[[26,"a"],[1,"b"],[18,"a"]]'
uncompress(output1)
//returns
"aaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaa"

//output2="abcde"
uncompress(output2)
//returns
"abcde"

Note: The original string may not contain "[]" for obvious reasons.