function _findLastIndex(arr, pred, ctx) {
  for (let i = arr.length - 1; i >= 0; --i) {
    if (pred.call(ctx, arr[i], i, arr)) {
      return i
    }
  }
  return -1
}
Finds the last index of a single element in an array matching `pred`.

@param {Array}    arr  - Array to search.
@param {Function} pred - Predicate function that returns `true` on matches.
@param {*}        ctx  - The `this` arg for `pred`.
@returns {number} - This index of the last matching item, or `-1`.