core-js/tests/unit-global/esnext.array.group.js

import { STRICT } from '../helpers/constants.js';

const { getPrototypeOf } = Object;

QUnit.test('Array#group', assert => {
  const { group } = Array.prototype;
  assert.isFunction(group);
  assert.arity(group, 1);
  assert.name(group, 'group');
  assert.looksNative(group);
  assert.nonEnumerable(Array.prototype, 'group');
  let array = [1];
  const context = {};
  array.group(function (value, key, that) {
    assert.same(arguments.length, 3, 'correct number of callback arguments');
    assert.same(value, 1, 'correct value in callback');
    assert.same(key, 0, 'correct index in callback');
    assert.same(that, array, 'correct link to array in callback');
    assert.same(this, context, 'correct callback context');
  }, context);
  assert.same(getPrototypeOf([].group(it => it)), null, 'null proto');
  assert.deepEqual([1, 2, 3].group(it => it % 2), { 1: [1, 3], 0: [2] }, '#1');
  assert.deepEqual(
    [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12].group(it => `i${ it % 5 }`),
    { i1: [1, 6, 11], i2: [2, 7, 12], i3: [3, 8], i4: [4, 9], i0: [5, 10] },
    '#2',
  );
  assert.deepEqual(Array(3).group(it => it), { undefined: [undefined, undefined, undefined] }, '#3');
  if (STRICT) {
    assert.throws(() => group.call(null, () => { /* empty */ }), TypeError, 'null this -> TypeError');
    assert.throws(() => group.call(undefined, () => { /* empty */ }), TypeError, 'undefined this -> TypeError');
  }
  array = [1];
  // eslint-disable-next-line object-shorthand -- constructor
  array.constructor = { [Symbol.species]: function () {
    return { foo: 1 };
  } };
  assert.same(array.group(Boolean).true.foo, undefined, 'no @@species');
});