Benchmark: undefined vs typeof vs in vs hasOwnProperty / ver. 2

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };
var keys = new Array(4096 * 5);
for (let i = 0; i < keys.length; i += 1)
  keys[i] = Math.random().toString();
for (let i = 0; i < keys.length; i += 2)
  obj[keys[i]] = i;

Tests:

undefined
for (let i = 0; i < 4096; i += 1) obj[keys[4096 * 0 + i]] === undefined;
typeof
for (let i = 0; i < 4096; i += 1) typeof obj[keys[4096 * 1 + i]] === "undefined";
in
for (let i = 0; i < 4096; i += 1) keys[4096 * 2 + i] in obj;
hasOwnProperty
for (let i = 0; i < 4096; i += 1) obj.hasOwnProperty(keys[4096 * 3 + i]);
bool
for (let i = 0; i < 4096; i += 1) !obj[keys[4096 * 4 + i]];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser/OS: Chrome 138 on Mac OS X 10.15.7

View result in a separate tab

undefined

10K/s

9K/s

typeof

9K/s

hasOwnProperty

6K/s

bool

5K/s

View exact numbers

Test name	Executions per second
✓ undefined	9,720 Ops/sec
in	9,175 Ops/sec
typeof	9,127 Ops/sec
hasOwnProperty	5,790 Ops/sec
bool	4,740 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case, specifically designed to measure the performance of different ways to check if a key is present in an object.

**Benchmark Definition**

The benchmark definition is specified by the "Script Preparation Code" and the individual test cases. The script preparation code creates an object `obj` with keys `a`, `b`, `c`, `d`, and `e`. It also generates an array of 20,000 random strings, `keys`, which will be used to access the object.

**Individual Test Cases**

There are five individual test cases:

1. **"undefined"`**: This test case checks if a key is present in the object by using the `obj[keys[4096 * 0 + i]]` expression. Since the value at this position is not defined, this test should return false.
2. **"typeof"`**: This test case checks if a key is present in the object by using the `typeof obj[keys[4096 * 1 + i]]` expression. Since the value at this position is not defined, this test should return "undefined".
3. **"in"`**: This test case checks if a key is present in the object by using the `keys[4096 * 2 + i] in obj` expression.
4. **"hasOwnProperty"`**: This test case checks if a key is present in the object by using the `obj.hasOwnProperty(keys[4096 * 3 + i])` expression.
5. **"bool"`**: This test case checks if a key is present in the object by using the `!obj[keys[4096 * 4 + i]]` expression.

**Options Compared**

The five test cases compare different ways to check if a key is present in an object:

*   Direct property access (`obj[keys[i]]`)
*   `typeof` operator
*   `in` keyword
*   `hasOwnProperty` method (only on objects)
*   Boolean negation (`!obj[key]`)

undefined vs typeof vs in vs hasOwnProperty / ver. 2 (version: 0) Benchmark.js

Object lookup performance

Comparing performance of: `undefined vs typeof vs in vs hasOwnProperty vs bool`

Created: 4 years ago by: Guest

Go to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

undefined vs typeof vs in vs hasOwnProperty / ver. 2 (version: 0) Benchmark.js

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool

Created: 4 years ago by: Guest

Go to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `undefined vs typeof vs in vs hasOwnProperty vs bool`