Convert array to string with ranges, ie: [1,2,3,5,6,8,10,11,13] -> "1-3,5-6,8,10-11,13"

109.js

function play(a,p) {
  s=''
  for (c in a)
    y=p==a[c]-1 ? s=s.slice(0,y ? -3 : -1)+'-' : 0,
    s+=(p=a[c])+','
  return s.slice(0,-1)
}

133.js

play=function p(a,m) {
  a=(a+'').replace(/(-\d+-)|((\d+),(\d+))/g, function(a,x,y,b,c) {
    return x ? m='-' : c-b-1 ? y : m=b+'-'+c
  })
  return m ? p(a) : a
}