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/*--- description: copyWithin and multi-level flat esid: sec-array.prototype.copywithin ---*/ assert.sameValue([1, 2, 3, 4, 5].copyWithin(0, 3).join(","), "4,5,3,4,5"); assert.sameValue([1, [2, [3, [4]]]].flat(2).join(","), "1,2,3,4"); assert.sameValue([1, [2], [3]].flat().length, 3);