str_to_time / time_to_str

str_to_time.coffee

# Convert string to a timestamp.
# str_to_time("01:20") = 80
str_to_time = (str) ->
  str.replace /^([0-9]{1,2}):([0-9]{2})$/, (t, m, s) -> (m* 60) + parseFloat(s)

time_to_str.coffee

# Convert a timestamp to a string.
# time_to_str(80) = "01:20"
time_to_str = (time) ->
  exp = /[0-9]{2}$/
  m = exp.exec('0' + Math.floor(time / 60))
  s = exp.exec('0' + Math.floor(time % 60))
  m.concat(s).join(':')