ironstrider

function fisherYates(array) {
  let i = array.length;
  let temp, j;
  
  while(i) {
    j = (Math.random() * i--) | 0;  // x | 0 gives floor(x)
    
    // swap elements i & j
    temp = array[i];
    array[i] = array[j];

ironstrider

// Returns the index of the last array element that satisfies a condition function. Otherwise, returns -1
// Similar to Array.prototype.findIndex, but finds the *last* element by searching from the right
// Parameters are exactly the same as findIndex:
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
function findLastIndex(array, callbackFn, thisArg) {
  for (let i = array.length - 1; i >= 0; i--) {
    if(callbackFn.call(thisArg, array[i], i, array)) {
      return i
    }