find index of last occurrence of token

find.coffee

bla = "qweronoquenr\n2424onounwerwer342342\nerw523535\n3534"

find_index_of_last = (instr, token) ->

    return null if not (token in instr)
    idx_shift = -1

    while true
        fd = instr.indexOf(token, idx_shift+1)
        if fd == -1
            return idx_shift

        idx_shift = fd


m = find_index_of_last(bla, "\n")
console.log(m)