Benchmark: instanceof vs typeof vs !!

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'
!!
obj.a

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
typeof
typeof no function
!!

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The provided JSON represents a benchmark that tests three different approaches to determine if an object is not null or undefined:

1. `instanceof` operator
2. `typeof` operator with a string comparison
3. The double exclamation mark (`!!`) operator

The benchmark creates an object `obj` with a single property `a`, which has the value 2.

**Options Compared**

The three options being compared are:

* `instanceof`: Checks if the object is an instance of the `Object` constructor.
* `typeof`: Returns the type of the object as a string. The comparison `typeof obj === 'object'` checks if the object is an object, but since JavaScript objects do not have a `constructor` property, this comparison can be ambiguous. However, in most cases, it will return `'object'`. The second comparison, `typeof obj === 'object' && typeof obj !== 'function'`, is specific to objects that are not functions.
* `!!`: This operator checks if the object is not null or undefined by converting it to a boolean value (truthy or falsy). In this case, since the object has a property `a` with a value of 2, it will be truthy.

**Pros and Cons**

Here's a brief overview of each option:

* `instanceof`: This method can be more reliable than `typeof`, as it directly checks if the object is an instance of a specific constructor. However, it may not work correctly for some objects, such as those created using `Object.create()`. Additionally, this method is less straightforward to understand and may require more browser support.
* `typeof`: This operator is widely supported and easy to read. It returns a string value that indicates the type of the object. The double negation (`!!`) operator can be used to convert this string to a boolean value. However, as mentioned earlier, it's not foolproof for objects without a constructor property.
* `!!`: This operator is simple and straightforward but may not provide the most accurate results if the object has multiple properties or values.

**Library Usage**

In this benchmark, there is no explicit library usage. However, some browsers like Chrome might use internal libraries to optimize their JavaScript engine performance.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark that require a deep understanding of the language.

**Other Alternatives**

Some alternative approaches could be:

* Using `Object.prototype.toString.call(obj)` to check if the object is an instance of the `Object` constructor.
* Using a library like `fast-check` or `benchmark.js` to perform more accurate and reliable benchmarking.
* Using a different testing framework, such as Jest or Mocha, which provides built-in support for benchmarks.

Keep in mind that these alternatives may have different pros and cons depending on the specific use case and requirements.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser/OS: Chrome 129 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
instanceof	8864094.0 Ops/sec
typeof	22400460.0 Ops/sec
typeof no function	11924350.0 Ops/sec
!!	22561318.0 Ops/sec

Related benchmarks:

instanceof vs typeof vs !! (version: 0)

Comparing performance of: instanceof vs typeof vs typeof no function vs !!

Created: one month ago by: Guest

Jump to the latest result

instanceof

typeof

typeof no function

!!

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):