Run results for: deep json spread vs flat

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser: Chrome 123

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
spread	7909334.5 Ops/sec
flat	4332786.0 Ops/sec

Script Preparation code:

var deepJson = [
  [{
	"items":
		{
			"item":
				[
					{
						"id": "0001",
						"type": "donut",
						"name": "Cake",
						"ppu": 0.55,
						"batters":
							{
								"batter":
									[
										{ "id": "1001", "type": "Regular" },
										{ "id": "1002", "type": "Chocolate" },
										{ "id": "1003", "type": "Blueberry" },
										{ "id": "1004", "type": "Devil's Food" }
									]
							},
						"topping":
							[
								{ "id": "5001", "type": "None" },
								{ "id": "5002", "type": "Glazed" },
								{ "id": "5005", "type": "Sugar" },
								{ "id": "5007", "type": "Powdered Sugar" },
								{ "id": "5006", "type": "Chocolate with Sprinkles" },
								{ "id": "5003", "type": "Chocolate" },
								{ "id": "5004", "type": "Maple" }
							]
					},

				]
		}
}],
  [{
	"items":
		{
			"item":
				[
					{
						"id": "0001",
						"type": "donut",
						"name": "Cake",
						"ppu": 0.55,
						"batters":
							{
								"batter":
									[
										{ "id": "1001", "type": "Regular" },
										{ "id": "1002", "type": "Chocolate" },
										{ "id": "1003", "type": "Blueberry" },
										{ "id": "1004", "type": "Devil's Food" }
									]
							},
						"topping":
							[
								{ "id": "5001", "type": "None" },
								{ "id": "5002", "type": "Glazed" },
								{ "id": "5005", "type": "Sugar" },
								{ "id": "5007", "type": "Powdered Sugar" },
								{ "id": "5006", "type": "Chocolate with Sprinkles" },
								{ "id": "5003", "type": "Chocolate" },
								{ "id": "5004", "type": "Maple" }
							]
					},

				]
		}
}]
]

Tests:

spread
const a = [...deepJson, ...deepJson, ...deepJson]
flat
const a = [deepJson, deepJson, deepJson].flat()