Benchmark: typeof vs isArray

Script Preparation code:

var value = 'something';
var c = 0;

Tests:

typeof
if (typeof value === 'string') { c++ }
isArray
if (Array.isArray(value)) { 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:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and the pros/cons of each approach.

**Benchmark Definition:**
The benchmark defines two test cases:

1. `typeof vs isArray`: This test case compares the execution performance of using `typeof` to check if a variable is a string versus using `Array.isArray()` to check if an object is an array.
2. Each test case has a simple script preparation code and HTML preparation code (which is empty in this case).

**Options Compared:**
The benchmark is comparing two approaches:

1. **`typeof`**: This method checks the type of a variable and returns a string indicating its type, such as `'string'`, `'number'`, or `'object'`.
2. **`Array.isArray()`**: This method checks if an object is an array by calling the `Array.prototype.isPrototypeOf()` method on it.

**Pros/Cons:**

1. **`typeof`**:
	* Pros:
		+ Simple and concise syntax.
		+ Works with most types, including functions and undefined values.
	* Cons:
		+ Can return unexpected results for certain types (e.g., `null`, `undefined`, `Symbol`).
		+ May be slower than `Array.isArray()` due to its complexity.
2. **`Array.isArray()`**:
	* Pros:
		+ Returns a boolean value, making it easy to use in conditional statements.
		+ More specific and accurate for checking array-like objects.
	* Cons:
		+ Only works with objects that have an `Array.prototype` prototype chain (most arrays).
		+ May be slower than `typeof` due to its method call.

**Library:**
There is no library used in this benchmark. The script and HTML preparation codes are simple and don't require any external libraries.

**Special JS Feature/Syntax:**
None of the test cases use any special JavaScript features or syntax beyond what's standard in modern JavaScript.

**Alternative Approaches:**

1. **Using `instanceof`**: Instead of `typeof`, you could use `instanceof` to check if a variable is an instance of a specific class (e.g., `Array`). However, this would require specifying the class name and might not be as concise.
2. **Using `TypeOf` functions**: Some JavaScript engines provide built-in `TypeOf` functions (e.g., in V8) that can check the type of a variable without using `typeof`. These functions are usually optimized for performance.
3. **Using polyfills or workarounds**: Depending on the specific use case, you might need to use polyfills or workarounds to achieve the desired behavior. For example, if you're targeting older browsers that don't support `Array.isArray()`, you might need to use a polyfill.

Keep in mind that these alternatives might not be as concise or performant as using the original methods (`typeof` and `Array.isArray()`), so they should only be considered when necessary.

Related benchmarks:

typeof vs isArray (version: 0)

Comparing performance of: typeof vs isArray

Created: 3 years ago by: Guest

Jump to the latest result

typeof

isArray

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):