Estimate JS interest

I have two variables.
let valMax = 29 let valNow = 15 let valEnter = ?
variable valMax No change, variable valNow Always change.
variables valEnter I need to get the result out as a percentage, How to explain to Javascript that 29 is 100%.

The simplest thing is
100 * текущее / максимальное
General formula
100 * (current  min) / (max  min)
a Reflecting borders and the inability to overcome them (in some cases no more than 100 per cent or less than 0 per cent)
(current < min) ? 0 : (current > max) ? 100 : (100 * (current  min) / (max  min))