JSTests/test262/test/built-ins/Array/prototype/some/15.4.4.17-7-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.some
es5id: 15.4.4.17-7-c-ii-5
description: >
    Array.prototype.some - k values are accessed during each iteration
    and not prior to starting the loop
---*/

        var kIndex = [];

        //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) {
            //Each position should be visited one time, which means k is accessed one time during iterations.
            if (typeof kIndex[idx] === "undefined") {
                //when current position is visited, its previous index should has been visited.
                if (idx !== 0 && typeof kIndex[idx - 1] === "undefined") {
                    return true;
                }
                kIndex[idx] = 1;
                return false;
            } else {
                return true;
            }
        }

assert.sameValue([11, 12, 13, 14].some(callbackfn, undefined), false, '[11, 12, 13, 14].some(callbackfn, undefined)');