Benchmark: instanceof vs typeof vs fast typeof object

Script Preparation code:

var obj = {a:2};

Tests:

instanceof
obj instanceof Object
typeof
typeof obj === 'object'
typeof object charAt
(typeof obj).charAt(0) === 'o'
typeof object slice
(typeof {}).slice(0,1) === 'o'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
typeof
typeof object charAt
typeof object slice

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 25 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36 Edg/131.0.0.0

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	4615432.5 Ops/sec
typeof	7939059.5 Ops/sec
typeof object charAt	7688023.0 Ops/sec
typeof object slice	91977704.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Overview**

The benchmark compares the performance of three approaches to check if an object is of type `Object`:

1. Using the `instanceof` operator
2. Using the `typeof` operator with the exact string `'object'`
3. Extracting the first character from the result of `typeof obj`

**Options Compared**

The options being compared are:

* `instanceof`: checks if an object is an instance of the specified constructor (in this case, `Object`)
* `typeof`: returns a string indicating the type of an object (e.g., `'object'` for objects)
* Extracting the first character from the result of `typeof obj`

**Pros and Cons**

1. **instanceof**: This approach is explicit and straightforward. It checks if the object is an instance of the specified constructor, which can be useful in certain scenarios. However, it may be slower than other approaches due to the overhead of invoking the constructor.
2. **typeof**: Using `typeof` with the exact string `'object'` is a common approach. It's fast and straightforward but may not work as expected if the object type changes or is not recognized by JavaScript.
3. Extracting the first character from `typeof obj`: This approach relies on the assumption that the result of `typeof obj` will always start with `'o'`. If this assumption is violated, it will produce incorrect results.

**Library and Purpose**

There is no explicit library mentioned in the benchmark definition or test cases. However, the use of `typeof` suggests that JavaScript's built-in type checking mechanism is being utilized.

**Special JS Feature or Syntax**

The benchmark does not appear to use any special JavaScript features or syntax beyond what's standard for JavaScript. It relies solely on the language's basic constructs and built-in functions.

**Other Considerations**

* The benchmark uses a simple object `obj` with a single property `a`, which is likely chosen to minimize variations in performance results.
* The test cases use a small, constant value (`obj`) to reduce variance and focus on the comparison between the three approaches.
* The benchmark results are provided for a specific browser and device platform (Mobile Safari 15 on iOS 15.1), which may limit the generalizability of the findings.

**Alternatives**

If you're interested in exploring alternative approaches, consider the following:

* Using `Object.prototype.toString.call(obj)` instead of `instanceof` or `typeof`. This approach uses the `toString()` method and `call()` to invoke a constructor function, which can be faster but may also introduce additional overhead.
* Implementing your own custom type checking mechanism using bitwise operations or regex patterns. However, this would likely require significant optimization and testing to ensure accuracy and performance.

Keep in mind that the choice of approach depends on the specific requirements and constraints of your project. The benchmark results should serve as a starting point for further exploration and optimization.

Related benchmarks:

instanceof vs typeof vs fast typeof object (version: 0)

Comparing performance of: instanceof vs typeof vs typeof object charAt vs typeof object slice

Created: 3 years ago by: Guest

Jump to the latest result

instanceof

typeof

typeof object charAt

typeof object slice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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