Benchmark: instanceof vs constructor name vs toString

Script Preparation code:

var toString = Object.prototype.toString
var isInstanceof = v => v && v instanceof Object
var isConstructorName = v => v?.constructor?.name === 'Object'
var isToString = v => toString.call(v) === '[object Object]'

Tests:

isInstanceof
isInstanceof({}) isInstanceof([]) isInstanceof(123) isInstanceof()
isConstructorName
isConstructorName({}) isConstructorName([]) isConstructorName(123) isConstructorName()
isToString
isToString({}) isToString([]) isToString(123) isToString()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
isInstanceof
isConstructorName
isToString

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested.

**Benchmark Definition**

The provided JSON defines three benchmark tests:

1. `instanceof`: Tests whether an object is an instance of the `Object` constructor using the `instanceof` operator.
2. `constructor name`: Tests whether a value has a `constructor` property with the name `'Object'`.
3. `toString`: Tests whether a value's string representation is `[object Object]`.

**Options Compared**

Each benchmark test compares different approaches:

* `isInstanceof` uses the built-in `instanceof` operator to check if an object is an instance of the `Object` constructor.
* `isConstructorName` uses a conditional expression (`v?.constructor?.name === 'Object'`) to check if a value has a `constructor` property with the name `'Object'`.
* `isToString` uses the `toString.call(v)` method to check if a value's string representation is `[object Object]`.

**Pros and Cons**

Here are some pros and cons of each approach:

1. `instanceof`:
	* Pros: Efficient, built-in operator.
	* Cons: May not work as expected for primitive values (e.g., numbers, strings) or functions.
2. `isConstructorName`:
	* Pros: Works with all types of values, including primitives and functions.
	* Cons: More complex expression, potentially slower due to optional chaining (`?.`).
3. `isToString`:
	* Pros: Works with all types of values, including primitives and functions.
	* Cons: May not be as efficient as `instanceof`, and the result may not be immediately apparent.

**Libraries**

None are explicitly used in this benchmark.

**Special JS Features or Syntax**

The only special feature used is optional chaining (`?.`) in the `isConstructorName` test. This syntax allows for safe navigation of nested properties without throwing errors if they don't exist.

**Other Considerations**

When choosing between these approaches, consider the specific requirements and constraints of your use case:

* If you need to check whether an object is an instance of a constructor, `instanceof` might be the best choice.
* If you need to check whether a value has a specific property with a certain name, `isConstructorName` might be suitable.
* If you need to check whether a value's string representation matches a specific pattern, `isToString` might be necessary.

**Alternatives**

Other alternatives for these approaches could include:

1. Using the `typeof` operator instead of `instanceof`.
2. Using a regular expression or string manipulation functions to compare string representations.
3. Using a library like Lodash's `isPlainObject` function to check if an object is a plain object.

Keep in mind that the choice of approach depends on the specific requirements and constraints of your use case, as well as personal preference and performance considerations.

Related benchmarks:

instanceof vs constructor name vs toString (version: 0)

Comparing performance of: isInstanceof vs isConstructorName vs isToString

Created: 2 years ago by: Registered User

Jump to the latest result

isInstanceof

isConstructorName

isToString

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):