swapIndex.js

let smallest = nums[i]
let swapIndex = i

// Search the remainder of the array for the smallest number
for (let j = i + 1; j < nums.length; j++) {
  if (nums[j] < smallest) {
    smallest = nums[j];
    swapIndex = j
  }
}

// Swap if the smallest number isn't at the current index
if (i !== swapIndex) {
  const tmp = nums[i]
  nums[i] = smallest
  nums[swapIndex] = tmp
}