Benchmark: instanceof vs typeof

Script Preparation code:

var obj = {a:2};

Tests:

instanceof
obj instanceof Object
typeof
typeof obj === 'object'
typeof no function
typeof obj === 'object' && typeof obj !== 'function'
typeof and test attribute
typeof obj === 'object' && obj.a

Historical Performance Data aggregated from 134 community runs

Desktop Results:

Chrome 107 runs

typeof

31.1M/s

typeof and test attribute

16.0M/s

typeof no function

15.9M/s

instanceof

11.9M/s

Fastest: typeof (2.6x faster)

View exact numbers

✓ typeof: 31,084,782 ops/sec
• typeof and test attribute: 16,025,359 ops/sec
• typeof no function: 15,903,741 ops/sec
• instanceof: 11,893,504 ops/sec

Firefox 14 runs

typeof

1466.7M/s

typeof no function

1208.3M/s

typeof and test attribute

1100.4M/s

instanceof

156.4M/s

Fastest: typeof (9.4x faster)

View exact numbers

✓ typeof: 1,466,747,520 ops/sec
• typeof no function: 1,208,324,096 ops/sec
• typeof and test attribute: 1,100,445,696 ops/sec
• instanceof: 156,356,032 ops/sec

Safari 5 runs

typeof

31.6M/s

typeof no function

20.1M/s

typeof and test attribute

17.6M/s

instanceof

13.7M/s

Fastest: typeof (2.3x faster)

View exact numbers

✓ typeof: 31,589,158 ops/sec
• typeof no function: 20,110,948 ops/sec
• typeof and test attribute: 17,595,160 ops/sec
• instanceof: 13,700,535 ops/sec

Mobile Results:

Chrome 8 runs

typeof

72.0M/s

typeof no function

69.4M/s

typeof and test attribute

65.0M/s

instanceof

60.8M/s

Fastest: typeof (1.2x faster)

View exact numbers

✓ typeof: 71,960,696 ops/sec
• typeof no function: 69,432,776 ops/sec
• typeof and test attribute: 65,042,920 ops/sec
• instanceof: 60,818,016 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
instanceof
typeof
typeof no function
typeof and test attribute

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/146.0.0.0 Safari/537.36

Browser/OS: Chrome 146 on Mac OS X 10.15.7

View result in a separate tab

instanceof

295.5M/s

typeof no function

284.7M/s

typeof and test attribute

273.1M/s

typeof

268.7M/s

View exact numbers

Test name	Executions per second
✓ instanceof	295,468,928 Ops/sec
typeof no function	284,713,824 Ops/sec
typeof and test attribute	273,132,032 Ops/sec
typeof	268,715,296 Ops/sec

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

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark that tests the performance of three different approaches to check if an object is an instance of a specific type or has a certain property.

In more detail, the benchmark compares the following:

1. `obj instanceof Object`: Checks if the object `obj` is an instance of the `Object` constructor.
2. `typeof obj === 'object'`: Uses the `typeof` operator to check if the type of `obj` is `'object'`.
3. `typeof obj === 'object' && typeof obj !== 'function'`: Combines checks from both 1 and 2, ensuring `obj` is an object but not a function.
4. `typeof obj === 'object' && obj.a`: Similar to the previous one, but also checks if `obj` has a property named `a`.

These approaches aim to evaluate the performance difference in checking object types or properties.

**Pros and Cons of each approach:**

1. **`obj instanceof Object`**: This approach is more accurate for checking if an object is of a specific type (in this case, `Object`). However, it may be slower due to the constructor call.
2. **`typeof obj === 'object'`**: This method is faster but less accurate, as it only checks the type of the object and does not account for its properties or prototype chain.
3. **`typeof obj === 'object' && typeof obj !== 'function'`**: This approach combines both speed and accuracy by checking the type and then verifying the absence of a function property. It's likely the fastest and most accurate option.
4. **`typeof obj === 'object' && obj.a`**: Similar to the previous one, but also checks if `obj` has a property named `a`. This approach is likely slower due to the additional check.

**Library usage**

There are no external libraries used in this benchmark. The tests only rely on built-in JavaScript features.

**Special JS feature or syntax**

None mentioned explicitly in the provided information. If present, it would be essential to note and discuss its relevance to the benchmark's results.

**Other alternatives**

Alternative approaches to check object types or properties include:

* Using a library like Lodash (`_.isPlainObject`, `_.isObject`) or Prototype Chain methods (`instanceof` with `Object.prototype.toString()`)
* Utilizing ES6 classes and instance checks
* Implementing custom getters or accessor functions

Keep in mind that each approach may have its trade-offs regarding performance, accuracy, and maintainability.

**Benchmark preparation code**

The provided script creates an object `obj` with a single property `a`. This simple object serves as the test subject for the benchmark's various checks.

In the context of this microbenchmark, these approaches are being compared to evaluate their relative performance on modern JavaScript engines.

instanceof vs typeof (version: 0)

Comparing performance of: `instanceof vs typeof vs typeof no function vs typeof and test attribute`

Created: 6 years ago by: Guest

Go to the latest result

instanceof

typeof

typeof no function

typeof and test attribute

Historical Performance Data aggregated from 134 community runs

Desktop Results:

Chrome 107 runs

Firefox 14 runs

Safari 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):

instanceof vs typeof (version: 0)

Comparing performance of: instanceof vs typeof vs typeof no function vs typeof and test attribute

Created: 6 years ago by: Guest

Go to the latest result

instanceof

typeof

typeof no function

typeof and test attribute

Historical Performance Data aggregated from 134 community runs

Desktop Results:

Chrome 107 runs

Firefox 14 runs

Safari 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: `instanceof vs typeof vs typeof no function vs typeof and test attribute`