JSTests/test262/test/built-ins/Array/prototype/filter/15.4.4.20-9-c-ii-5.js

// Copyright (c) 2012 Ecma International.  All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/*---
esid: sec-array.prototype.filter
description: >
    Array.prototype.filter - k values are accessed during each
    iteration and not prior to starting the loop on an Array
---*/

var kIndex = [];
var called = 0;

//By below way, we could verify that k would be setted as 0, 1, ..., length - 1 in order, and each value will be setted one time.
function callbackfn(val, idx, obj) {
  called++;
  //Each position should be visited one time, which means k is accessed one time during iterations.
  if (kIndex[idx] === undefined) {
    //when current position is visited, its previous index should has been visited.
    if (idx !== 0 && kIndex[idx - 1] === undefined) {
      return true;
    }
    kIndex[idx] = 1;
    return false;
  } else {
    return true;
  }
}
var newArr = [11, 12, 13, 14].filter(callbackfn, undefined);

assert.sameValue(newArr.length, 0, 'newArr.length');
assert.sameValue(called, 4, 'called');