Benchmark: isArray plus name

Script Preparation code:

var toStr = Object.prototype.toString
	
function toStrCase(obj){
  return toStr.call(obj) === '[object Array]'
}
function consCase(obj){
  return obj.constructor === Array
}
function instCase(obj){
  return obj instanceof Array
}
function consCaseName(obj){
  return obj.constructor.name === 'Array'
}
var isArray = Array.isArray

Tests:

Array.isArray
isArray([])
instanceof
instCase([])
[].constructor
consCase([])
Object.prototype.toString
toStrCase([])
[].constructor.name
consCaseName([])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.isArray
instanceof
[].constructor
Object.prototype.toString
[].constructor.name

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.67 Safari/537.36

Browser/OS: Chrome 87 on Mac OS X 10.11.6

View result in a separate tab

Test name	Executions per second
Array.isArray	6561377.0 Ops/sec
instanceof	2230753.0 Ops/sec
[].constructor	2243595.8 Ops/sec
Object.prototype.toString	2910358.0 Ops/sec
[].constructor.name	5061853.5 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 test cases and explain what's being tested, along with their pros and cons.

**Overview**

The benchmark compares the performance of four different ways to check if an object is an array:

1. `Array.isArray`
2. `Object.prototype.toString` with a custom implementation (`toStrCase`)
3. `[]`.constructor`
4. `instanceof Array`

**Options Comparison**

Here's a brief overview of each option:

### 1. `Array.isArray`

`Array.isArray` is a built-in method that checks if an object is an array. It's the most straightforward way to check, but it may have some performance implications due to its method call overhead.

Pros: Simple and easy to understand.
Cons: May have performance overhead due to method call.

### 2. `Object.prototype.toString`

`Object.prototype.toString` is a built-in method that returns a string representation of an object. By comparing this string with the string '[object Array]', we can determine if the object is an array. This approach requires some custom implementation (`toStrCase`) to make it work.

Pros: Can be faster than `Array.isArray` since it's a simple comparison.
Cons: Requires additional code and may have performance overhead due to method call.

### 3. `[].constructor`

In JavaScript, every object has a `constructor` property that points to its constructor function. Since arrays are created using the `[]` syntax, their constructors are also arrays. By checking if the `constructor` is an array, we can determine if it's an array.

Pros: Simple and easy to understand.
Cons: May have performance overhead due to method call.

### 4. `instanceof Array`

The `instanceof` operator checks if an object is an instance of a given constructor function. By using `Array`, we can check if the object is an array.

Pros: Can be faster than other methods since it's a direct comparison.
Cons: Requires careful implementation to ensure correct behavior.

**Library and Special JS Features**

None of these options rely on any external libraries or special JavaScript features (e.g., ES6 classes, async/await).

**Other Considerations**

When writing performance benchmarks like this one, it's essential to consider the following:

* Warm-up time: Make sure the benchmark runs long enough to warm up the browser and ensure accurate results.
* Consistency: Ensure that all test cases are executed consistently across different browsers and devices.
* Noise reduction: Filter out noise from the benchmark results (e.g., network latency, rendering times) to get a clean picture of performance.

**Alternatives**

If you need to compare other ways to check if an object is an array, consider exploring these options:

* Using `typeof` instead of `Array.isArray`
* Creating a custom implementation using bitwise operations
* Using a library like Lodash or Underscore.js for array checks

Keep in mind that each approach has its pros and cons, and the best choice depends on your specific use case and performance requirements.

Related benchmarks:

isArray plus name (version: 0)

Array.isArray vs Object.prototype.toString vs [].constructor vs instanceof

Comparing performance of: Array.isArray vs instanceof vs [].constructor vs Object.prototype.toString vs [].constructor.name

Created: 4 years ago by: Guest

Jump to the latest result

Array.isArray

instanceof

[].constructor

Object.prototype.toString

[].constructor.name

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):