Which takes less execution time?

Question

Which would take less execution time; a switch-case or an equation?

I want to make a page dim more the more cascading windows are appearing one on top of the other like pop-ups.

So if I have 1 child window; the dimming percentage could be 20%, 2 child windows; 40%; 4 child windows; 50% .. and so and so, so it gets less darker as the window cascades and eventually stops at a certain value, for example 55%, so it is never too dark.

The equation it should follow is: f(x) = 5x^4/8 - 65x^3/12 + 95x^2/8 + 155x/12

This should give values as follow:

f(x) |  0  | 20 | 40 | 50 | 55 |
  x  |  0  |  1 |  2 |  3 |  4 |

Domain of x = [0,4]

Whereas; f(x) = needed mount of dimming and x is the number of windows cascading

Is that a better implementation in terms of execution time; or would a switch-case be better for comparing the current number of windows opened against the needed dimming percentage?

I don't know how many instructions are used per the switch case versus the equation mentioned above?

Answer 1

If performance is really an issue, don't use switch or an equation. Use an array.

function f(x) {
    const dim_pct = [0, 20, 40, 50, 55];
    return dim_pct[x];
}