I've just been putting together an audio meter by stacking bootstrap progress bars, and thought there was probably a better way, mathematically / logically, of achieving this.
levels = (vumeter) ->
green = if vumeter % 50 < vumeter then 50 else vumeter
yellow = if vumeter % 85 < vumeter then 35 else vumeter - 50
red = if vumeter % 100 < vumeter then 15 else vumeter - 85
'green': green
'yellow': yellow
'red': red
Assuming that you want to replicate a classical audio meter (aka green bar grows until 50, then a yellow bar appears on top of green and grows until 85, then a red bar grows from there), then the easiest way to do this is with min and max functions.
Assuming that vumeter should not be mutated here is the pseudo-code I came up with:
green = min(vumeter, 50)
yellow = max(min(vumeter - green, 35), 0)
red = max(min(vumeter - green - yellow, 15), 0)
vumeter % 50 < vumeter doesn't make much sense to me. For non-negative numbers, this is equivalent to vumeter > 50, so you can just use that instead. For negative numbers, this will always return false, although it seems like this would be an illegal argument to your function.
@mleyfman provided a great solution. In practice, the code provided achieves something called clamping, where you restrict a value to a specified range. You can roll your own clamp function like so:
clamp = (value, min, max) -> Math.min(Math.max(min, value), max)
levels = (vumeter) ->
'green' : clamp(vumeter, 0, 50)
'yellow' : clamp(vumeter, 50, 85) - 50
'red' : clamp(vumeter, 85, 100) - 85
// or, if you find it more meaningful to provide maxima as parameters rather than ranges:
'green': clamp(vumeter, 0, 50)
'yellow': clamp(vumeter - 50, 0, 35)
'red': clamp(vumeter - 85, 0, 15)
