Run-length encoding

You are encouraged to solve this task according to the task description, using any language you may know.


Task

Given a string containing uppercase characters (A-Z), compress repeated 'runs' of the same character by storing the length of that run, and provide a function to reverse the compression.

The output can be anything, as long as you can recreate the input with it.



Example

 Input: WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW
 Output: 12W1B12W3B24W1B14W


Note: the encoding step in the above example is the same as a step of the Look-and-say sequence.




encode = (str) ->
    str.replace /(.)\1*/g, (w) ->
        w[0] + w.length
 
decode = (str) ->
    str.replace /(.)(\d+)/g, (m,w,n) ->
        new Array(+n+1).join(w)
 
console.log s = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
console.log encode s
console.log decode encode s