Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;

Historical Performance Data aggregated from 140 community runs

Desktop Results:

Chrome 110 runs

typeof

28.5M/s

28.4M/s

bool

28.3M/s

hasOwnProperty

24.9M/s

undefined

11.1M/s

Fastest: typeof (2.6x faster)

View exact numbers

✓ typeof: 28,530,258 ops/sec
• in: 28,447,060 ops/sec
• bool: 28,251,338 ops/sec
• hasOwnProperty: 24,852,876 ops/sec
• undefined: 11,143,366 ops/sec

Firefox 11 runs

typeof

973.4M/s

900.4M/s

hasOwnProperty

873.6M/s

bool

863.7M/s

undefined

829.0M/s

Fastest: typeof (1.2x faster)

View exact numbers

✓ typeof: 973,419,200 ops/sec
• in: 900,442,496 ops/sec
• hasOwnProperty: 873,620,032 ops/sec
• bool: 863,692,608 ops/sec
• undefined: 829,036,352 ops/sec

Safari 6 runs

typeof

31.8M/s

31.6M/s

bool

31.6M/s

hasOwnProperty

31.1M/s

undefined

11.2M/s

Fastest: typeof (2.8x faster)

View exact numbers

✓ typeof: 31,798,612 ops/sec
• in: 31,601,492 ops/sec
• bool: 31,559,964 ops/sec
• hasOwnProperty: 31,145,356 ops/sec
• undefined: 11,197,392 ops/sec

Other 5 runs

typeof

254.6M/s

bool

252.9M/s

242.5M/s

undefined

234.6M/s

hasOwnProperty

152.9M/s

Fastest: typeof (1.7x faster)

View exact numbers

✓ typeof: 254,636,880 ops/sec
• bool: 252,883,760 ops/sec
• in: 242,479,632 ops/sec
• undefined: 234,631,296 ops/sec
• hasOwnProperty: 152,875,264 ops/sec

Mobile Results:

Chrome 8 runs

typeof

18.7M/s

bool

18.7M/s

18.5M/s

hasOwnProperty

16.1M/s

undefined

7.5M/s

Fastest: typeof (2.5x faster)

View exact numbers

✓ typeof: 18,676,362 ops/sec
• bool: 18,654,818 ops/sec
• in: 18,471,200 ops/sec
• hasOwnProperty: 16,105,794 ops/sec
• undefined: 7,504,119 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
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:138.0) Gecko/20100101 Firefox/138.0

Browser/OS: Firefox 138 on Windows

View result in a separate tab

730.8M/s

hasOwnProperty

708.2M/s

undefined

695.0M/s

typeof

663.7M/s

bool

657.7M/s

View exact numbers

Test name	Executions per second
✓ in	730,780,288 Ops/sec
hasOwnProperty	708,181,056 Ops/sec
undefined	694,998,080 Ops/sec
typeof	663,690,048 Ops/sec
bool	657,673,536 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided benchmark measures the performance of different JavaScript operators for object lookup: `undefined`, `typeof`, `in`, `hasOwnProperty`, and a boolean test (`!! obj.d;`).

**Operator Comparison**

Here's an explanation of each operator, their pros and cons, and alternative approaches:

1. **Undefined (`undefined !== obj.d;`)**
	* This operator checks if the variable `obj.d` has been assigned a value (i.e., is not `undefined`). It's often used to avoid errors when accessing object properties.
	* Pros: Simple and straightforward.
	* Cons: Can be slower due to the explicit check.
	* Alternative approach: Use the optional chaining operator (`?.`) introduced in ECMAScript 2020, which allows safe navigation of nested objects without throwing an error. Example: `obj?.d;`
2. **typeof (`'undefined' !== typeof obj.d;`)**
	* This operator checks if the type of `obj.d` is indeed `undefined`.
	* Pros: More explicit and safer than using the `===` operator.
	* Cons: Can be slower due to the additional comparison.
	* Alternative approach: Use the optional chaining operator (`?.`) instead, which provides similar functionality without the need for `typeof`. Example: `'?' in obj;`
3. **in (`'d' in obj;`)**
	* This operator checks if the property `'d'` exists in the object `obj`.
	* Pros: Similar to `hasOwnProperty`, but returns a boolean value.
	* Cons: Can be slower due to the additional lookup.
	* Alternative approach: Use the optional chaining operator (`?.`) instead, which provides similar functionality without the need for `in`. Example: `obj['d'] !== undefined;`
4. **hasOwnProperty (`obj.hasOwnProperty( 'd' );`)**
	* This operator checks if the property `'d'` exists in the object `obj` and was not inherited from a parent object.
	* Pros: More accurate than using `in`, as it excludes inherited properties.
	* Cons: Can be slower due to the additional check.
	* Alternative approach: Use the optional chaining operator (`?.`) instead, which provides similar functionality without the need for `hasOwnProperty`. Example: `obj['d'] !== undefined;`

**Library and Special JS Features**

The benchmark uses no external libraries or special JavaScript features. The only notable feature is the use of `!! obj.d;`, which is a boolean test that evaluates to `true` if `obj.d` has any truthy value (e.g., number, string, object). This test is not specific to any particular library or syntax.

**Other Alternatives**

Some alternative approaches for object lookup can be found in other languages:

* In Python, you would use the `.get()` method: `obj.get('d', None)`
* In Java, you would use the `instanceof` operator: `obj instanceof Object && obj instanceof MyObject`

Keep in mind that these alternatives may have different performance characteristics and are not directly equivalent to the JavaScript operators being tested.

**Benchmark Conclusion**

The benchmark provides a good overview of the performance differences between various object lookup methods in JavaScript. However, it's essential to note that the results may vary depending on specific use cases, object structures, and browser implementations.

undefined vs. typeof vs. in vs. hasOwnProperty (version: 0)

Object lookup performance

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

Created: 9 years ago by: Guest

Go to the latest result

undefined

typeof

in

hasOwnProperty

bool

Historical Performance Data aggregated from 140 community runs

Desktop Results:

Chrome 110 runs

Firefox 11 runs

Safari 6 runs

Other 5 runs

Mobile Results:

Chrome 8 runs

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 (version: 0)

Object lookup performance

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

Created: 9 years ago by: Guest

Go to the latest result

undefined

typeof

in

hasOwnProperty

bool

Historical Performance Data aggregated from 140 community runs

Desktop Results:

Chrome 110 runs

Firefox 11 runs

Safari 6 runs

Other 5 runs

Mobile Results:

Chrome 8 runs

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`