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/* eslint-disable no-sparse-arrays, unicorn/prefer-array-flat -- required for testing */
QUnit.test('Array#concat', assert => {
const { concat } = Array.prototype;
assert.isFunction(concat);
assert.arity(concat, 1);
assert.name(concat, 'concat');
assert.looksNative(concat);
assert.nonEnumerable(Array.prototype, 'concat');
let array = [1, 2];
const sparseArray = [1, , 2];
const nonSpreadableArray = [1, 2];
nonSpreadableArray[Symbol.isConcatSpreadable] = false;
const arrayLike = { 0: 1, 1: 2, length: 2 };
const spreadableArrayLike = { 0: 1, 1: 2, length: 2, [Symbol.isConcatSpreadable]: true };
assert.deepEqual(array.concat(), [1, 2], '#1');
assert.deepEqual(sparseArray.concat(), [1, , 2], '#2');
assert.deepEqual(nonSpreadableArray.concat(), [[1, 2]], '#3');
assert.deepEqual(concat.call(arrayLike), [{ 0: 1, 1: 2, length: 2 }], '#4');
assert.deepEqual(concat.call(spreadableArrayLike), [1, 2], '#5');
assert.deepEqual([].concat(array), [1, 2], '#6');
assert.deepEqual([].concat(sparseArray), [1, , 2], '#7');
assert.deepEqual([].concat(nonSpreadableArray), [[1, 2]], '#8');
assert.deepEqual([].concat(arrayLike), [{ 0: 1, 1: 2, length: 2 }], '#9');
assert.deepEqual([].concat(spreadableArrayLike), [1, 2], '#10');
assert.deepEqual(array.concat(sparseArray, nonSpreadableArray, arrayLike, spreadableArrayLike), [
1, 2, 1, , 2, [1, 2], { 0: 1, 1: 2, length: 2 }, 1, 2,
], '#11');
array = [];
// eslint-disable-next-line object-shorthand -- constructor
array.constructor = { [Symbol.species]: function () {
return { foo: 1 };
} };
assert.same(array.concat().foo, 1, '@@species');
});
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