JSTests/test262/test/built-ins/Array/prototype/filter/15.4.4.20-6-8.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
es5id: 15.4.4.20-6-8
description: >
    Array.prototype.filter returns an empty array if 'length' is 0
    (subclassed Array, length overridden with []
---*/

  foo.prototype = new Array(1, 2, 3);
  function foo() {}
  var f = new foo();

  f.length = [];

  // 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.

  function cb(){}
  var a = f.filter(cb);


assert(Array.isArray(a), 'Array.isArray(a) !== true');
assert.sameValue(a.length, 0, 'a.length');