I have an array of fixed or randomized distance values, multiplied by the scale of a map, mapScale. The randomized values can be generated using function randomNum(num1, num2).

I am looking to assign to variable distance a new value, for each iteration within a loop, using a pre-determined distances array index position. The array index position value should remain the same for each iteration within the loop (ex: 6), but the distance value should change for each iteration if the array element is a randomized number for the specified index position.

Please note that if a "randomization" index position is specified, I do want to get a new randomized number for each iteration (ex: 6.22, 7.08, 9.45, etc.) and not simply a constant pre-determined one (ex: 7.84).

The following code works, but calling randomNum for each iteration is probably not optimal, especially since we already know the index position of the element we are looking to retrieve. Please also note that the number of iterations, n, varies from about 500 to roughly 10,000.

var indexPosition = findIndexPosition(...)

for (let i = 0; i <= n; i++){   

   var distances = [
      mapscale * 0.25,
      mapscale * 0.75,
      mapscale * 1,
      mapscale * 1.5,
      mapscale * 2,
      mapscale * randomNum(3, 5),
      mapscale * randomNum(6, 10),
      mapscale * randomNum(15, 50),
      mapscale * randomNum(100, 500),
      mapscale * randomNum(1000, 2500),
   ];

   var distance = distances[indexPosition]

   [...]
 }      

I would like to find the most elegant solution (optimal speed / number of line balance) to achieve the desired behavior. I am open to using a switch statement, a function, object, etc., as long as the code remains concise and the performance is optimized.