Benchmark: instanceof vs typeof for objects

Script Preparation code:

var obj = {a:1}

Tests:

instanceof
obj instanceof Object
typeof
typeof obj === 'object' && obj !== null

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
typeof

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided JSON and explain what is being tested, compared, and considered.

**Benchmark Definition**

The provided JSON represents a benchmark definition for comparing two approaches:

1. `obj instanceof Object`
2. `typeof obj === 'object' && obj !== null`

Both tests are designed to check if an object (`obj`) is of type `Object` using different methods: the `instanceof` operator and a string comparison.

**What's being tested?**

In essence, these two tests aim to measure:

* Which approach is faster for checking if an object is of type `Object`: using the `instanceof` operator or a string comparison with `typeof` followed by a negation (`obj !== null`).
* The overhead and performance differences between these two approaches.

**Options compared**

The two options being compared are:

1. **`instanceof` operator**: This operator checks if an object is of a specific class (in this case, `Object`). It's a built-in JavaScript operator that returns `true` if the object is an instance of the specified class and `false` otherwise.
2. **String comparison with `typeof` and negation**: This approach involves using `typeof` to check if the object is of type `'object'`, followed by a negation (`obj !== null`) to exclude `null` values.

**Pros and Cons**

* **`instanceof` operator**:
	+ Pros: Direct, efficient way to check if an object is of a specific class.
	+ Cons: May be slower for certain use cases due to the overhead of dynamic typing and object lookup in V8 (Chrome's JavaScript engine).
* **String comparison with `typeof` and negation**:
	+ Pros: More flexible, as it can be used with any type, not just classes.
	+ Cons: Requires an extra step to negate the result (`obj !== null`) and may involve more overhead due to string comparison.

**Library usage**

There is no library explicitly mentioned in the provided JSON. However, the `typeof` operator uses a library called `V8` (Chrome's JavaScript engine), which provides the implementation for this operator.

**Special JS feature or syntax**

The `instanceof` operator is a built-in JavaScript feature that checks if an object is of a specific class. There are no special features or syntaxes mentioned in the provided JSON.

**Other alternatives**

Alternative approaches to checking if an object is of type `Object` might include:

* Using a library like Lodash, which provides a `isPlainObject()` function.
* Implementing a custom function using a bitwise check (`obj === Object.prototype && obj !== null`) or recursion.
* Using a different data structure, like a `Map`, to store objects and then checking if an object is present in the map.

Keep in mind that these alternatives might not be as efficient or straightforward as using the `instanceof` operator or string comparison with `typeof` and negation.

Related benchmarks:

instanceof vs typeof for objects (version: 0)

Comparing performance of: instanceof vs typeof

Created: 3 years ago by: Guest

Jump to the latest result

instanceof

typeof

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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