Benchmark: Add item to array: push vs spread vs assign vs items.length vs items[len++]

Add item to array: push vs spread vs assign vs items.length vs items[len++] (version: 7)

Comparing performance of: `Push item to an array vs Append an item by spread vs Direct assign an item to an initialized array vs items[items.length] vs items[items.length] outer length counter vs items[items.length] outer length counter + new Array() vs Cutting empty tail`

Created: one year ago by: Registered User

Go to the latest result

Script Preparation code:

window.MAX_SIZE = 1000;

Tests:

Push item to an array
const items = []; for (let i = 0; i < MAX_SIZE; i++) { items.push(Math.random()); }
Append an item by spread
let items = []; for (let i = 0; i < MAX_SIZE; i++) { items = [...items, Math.random()]; }
Direct assign an item to an initialized array
const items = new Array(MAX_SIZE); for (let i = 0; i < MAX_SIZE; i++) { items[i] = Math.random();; }
items[items.length]
const items = []; for (let i = 0; i < MAX_SIZE; i++) { items[items.length] = Math.random(); }
items[items.length] outer length counter
const items = []; let len = 0; while (len < MAX_SIZE) { items[len++] = Math.random(); }
items[items.length] outer length counter + new Array()
const items = new Array(MAX_SIZE); let len = 0; while (len < MAX_SIZE) { items[len++] = Math.random(); }
Cutting empty tail
const items = new Array(1500); let len = 0; while (len < MAX_SIZE) { items[len++] = Math.random(); } items.length = MAX_SIZE;

Historical Performance Data aggregated from 8 community runs

Desktop Results:

Chrome 8 runs

Direct assign an item to an initialized array

112K/s

items[items.length] outer length counter + new Array()

110K/s

items[items.length] outer length counter

76K/s

items[items.length]

72K/s

Push item to an array

50K/s

Append an item by spread

625/s

Fastest: Direct assign an item to an initialized array (179.8x faster)

View exact numbers

✓ Direct assign an item to an initialized array: 112,368 ops/sec
• items[items.length] outer length counter + new Array(): 109,864 ops/sec
• items[items.length] outer length counter: 75,746 ops/sec
• items[items.length]: 72,292 ops/sec
• Push item to an array: 50,079 ops/sec
• Append an item by spread: 625 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Push item to an array
Append an item by spread
Direct assign an item to an initialized array
items[items.length]
items[items.length] outer length counter
items[items.length] outer length counter + new Array()
Cutting empty tail

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3424.0 Safari/537.36

Browser/OS: Chrome 68 on Linux

View result in a separate tab

Direct assign an item to an initialized array

74K/s

items[items.length] outer length counter + new Array()

71K/s

Cutting empty tail

64K/s

items[items.length]

45K/s

items[items.length] outer length counter

45K/s

Push item to an array

36K/s

Append an item by spread

66/s

View exact numbers

Test name	Executions per second
✓ Direct assign an item to an initialized array	74,115 Ops/sec
items[items.length] outer length counter + new Array()	71,488 Ops/sec
Cutting empty tail	64,241 Ops/sec
items[items.length]	44,867 Ops/sec
items[items.length] outer length counter	44,741 Ops/sec
Push item to an array	36,145 Ops/sec
Append an item by spread	66 Ops/sec

Add item to array: push vs spread vs assign vs items.length vs items[len++] (version: 7)

Comparing performance of: Push item to an array vs Append an item by spread vs Direct assign an item to an initialized array vs items[items.length] vs items[items.length] outer length counter vs items[items.length] outer length counter + new Array() vs Cutting empty tail

Created: one year ago by: Registered User

Go to the latest result

Push item to an array

Append an item by spread

Direct assign an item to an initialized array

items[items.length]

items[items.length] outer length counter

items[items.length] outer length counter + new Array()

Cutting empty tail

Historical Performance Data aggregated from 8 community runs

Desktop Results:

Chrome 8 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Related benchmarks

Comparing performance of: `Push item to an array vs Append an item by spread vs Direct assign an item to an initialized array vs items[items.length] vs items[items.length] outer length counter vs items[items.length] outer length counter + new Array() vs Cutting empty tail`