Benchmark: Array isArray vs typeof

Script Preparation code:

var test = [1,2,3,4];
var c;

Tests:

typeof
if (typeof test === 'object') { c++; }
isArray
if (Array.isArray(test)) { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
isArray

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 15 days ago)

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 134 on Android

View result in a separate tab

Test name	Executions per second
typeof	2985782.0 Ops/sec
isArray	3070768.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

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

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark created on MeasureThat.net. The benchmark compares two approaches for checking if an array is present in the variable `test`. The variable `test` is initialized with an array `[1,2,3,4]`.

**Options compared:**

Two options are compared:

1. **typeof**: This option uses the `typeof` operator to check if `test` is an object. In JavaScript, the `typeof` operator returns a string indicating the type of the operand. If `test` is an array, `typeof test` will return `"object"`.
2. **Array.isArray()**: This option uses the built-in `Array.isArray()` method to check if `test` is an array.

**Pros and Cons:**

* **typeof**: Pros:
	+ Lightweight and fast.
	+ Works for non-array values that also have an "object" prototype (e.g., objects, functions).
Cons:
	+ Returns `"object"` for arrays, which can lead to incorrect results if the code assumes only arrays are objects.
	+ Not specifically designed for array checking.
* **Array.isArray()**: Pros:
	+ Specifically designed for array checking and returns `true` or `false`.
Cons:
	+ May be slower than `typeof` due to the additional function call.

**Other considerations:**

Both options have their trade-offs. Using `typeof` is a more lightweight approach, but it can lead to incorrect results if not handled carefully. Using `Array.isArray()` provides a clear and specific result, but may incur a slight performance penalty.

**Library used (if any):**

There are no libraries explicitly mentioned in the provided benchmark. However, some JavaScript implementations might use internal libraries or optimizations that affect the behavior of these operators.

**Special JS features or syntax:**

There are no special JS features or syntax mentioned in this benchmark. The code uses standard JavaScript syntax and built-in functions.

**Benchmark result interpretation:**

The latest benchmark results show that:

* The `typeof` approach has a higher execution frequency (7165740.5 executions per second) compared to the `Array.isArray()` approach (5344501.0 executions per second).
* This suggests that the `typeof` approach is likely faster and more efficient for this particular test case.

**Alternatives:**

Other alternatives for checking if an array is present in a variable might include:

* Using the `instanceof` operator, which checks if an object is an instance of a specific constructor (e.g., Array).
* Using a custom function or helper that implements both `typeof` and `Array.isArray()` behaviors.
* Using a library or framework-specific solution for array checking.

Keep in mind that these alternatives might introduce additional overhead or complexity, depending on the specific use case.

Related benchmarks:

Array isArray vs typeof (version: 0)

Comparing performance of: typeof vs isArray

Created: 4 years ago by: Guest

Jump to the latest result

typeof

isArray

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):