core-js/internals/array-iteration-from-last.js

'use strict';
var bind = require('../internals/function-bind-context');
var IndexedObject = require('../internals/indexed-object');
var toObject = require('../internals/to-object');
var lengthOfArrayLike = require('../internals/length-of-array-like');

// `Array.prototype.{ findLast, findLastIndex }` methods implementation
var createMethod = function (TYPE) {
  var IS_FIND_LAST_INDEX = TYPE === 1;
  return function ($this, callbackfn, that) {
    var O = toObject($this);
    var self = IndexedObject(O);
    var index = lengthOfArrayLike(self);
    var boundFunction = bind(callbackfn, that);
    var value, result;
    while (index-- > 0) {
      value = self[index];
      result = boundFunction(value, index, O);
      if (result) switch (TYPE) {
        case 0: return value; // findLast
        case 1: return index; // findLastIndex
      }
    }
    return IS_FIND_LAST_INDEX ? -1 : undefined;
  };
};

module.exports = {
  // `Array.prototype.findLast` method
  // https://github.com/tc39/proposal-array-find-from-last
  findLast: createMethod(0),
  // `Array.prototype.findLastIndex` method
  // https://github.com/tc39/proposal-array-find-from-last
  findLastIndex: createMethod(1)
};