JSTests/test262/test/built-ins/Array/prototype/forEach/15.4.4.18-8-9.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.foreach
description: >
    Array.prototype.forEach doesn't call callbackfn if 'length' is 0
    (subclassed Array, length overridden with [0]
---*/

foo.prototype = new Array(1, 2, 3);

function foo() {}
var f = new foo();

f.length = [0];

// objects inherit the default valueOf method of the Object object;
// that simply returns the itself. Since the default valueOf() method
// does not return a primitive value, ES next tries to convert the object
// to a number by calling its toString() method and converting the
// resulting string to a number.
//
// The toString( ) method on Array converts the array elements to strings,
// then returns the result of concatenating these strings, with commas in
// between. An array with no elements converts to the empty string, which
// converts to the number 0. If an array has a single element that is a
// number n, the array converts to a string representation of n, which is
// then converted back to n itself. If an array contains more than one element,
// or if its one element is not a number, the array converts to NaN.

var callCnt = 0;

function cb() {
  callCnt++
}
var i = f.forEach(cb);

assert.sameValue(callCnt, 0, 'callCnt');