/**
 * Find the index of a single value from an array of values, based on criteria defined in a predicate function.
 *
 * @function
 * @name findIndex
 * @param {function} pred A predicate function to apply to the array of values (It should take a val as input and return a Boolean as output).
 * @param {Array<*>} arr An array of values from which to find the index of one particular matching value
 * @returns {number} Either the index of the value from the array that matched the predicate function or negative one (-1, if no match).
 */
function findIndex(pred, arr) {
  let i = -1
  const len = arr.length
  while (++i < len) {
    if (pred(arr[i])) return i
  }
  return -1
}

export default findIndex