Benchmark: Array.isArray(array) vs. typeof string

Script Preparation code:

const arr = ["foo"];
const str = "foo";

Tests:

Array.isArray(arr)
Array.isArray(arr)
typeof str === string
typeof str === 'string'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.isArray(arr)
typeof str === string

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Array.isArray(arr)	132490712.0 Ops/sec
typeof str === string	164620320.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON focuses on comparing two different methods for checking the type of a variable in JavaScript: `Array.isArray()` and `typeof`. Specifically, it is testing whether an array is correctly identified as such using `Array.isArray(arr)` versus determining if a string is indeed a string with `typeof str === 'string'`.

### Options Compared

1. **`Array.isArray(arr)`**
   - This method is specifically designed to check if a given variable is an Array. It returns `true` if the variable is an array and `false` otherwise.

2. **`typeof str === 'string'`**
   - This is a type checking mechanism that utilizes the `typeof` operator to ascertain if the variable `str` is of type string. It returns `true` when `str` is indeed a string.

### Pros and Cons

**`Array.isArray(arr)`**
- **Pros**:
  - Explicitly checks for array types, making the code more readable and clear.
  - Handles edge cases correctly (e.g., `Array.isArray(null)` returns `false`, which is expected behavior).
  - Faster than some alternatives (like checking the constructor or using `instanceof`) because it is a native function optimized for this purpose.

- **Cons**:
  - Limited to checking only for arrays; it does not evaluate other types.

**`typeof str === 'string'`**
- **Pros**:
  - Simple and straightforward syntax for checking type, working well with primitive types.
  - Widely used and understood, making it easily recognizable to most developers.
  - Provides direct information about the type of the variable.

- **Cons**:
  - It returns `'object'` for some values like `null`, which may cause confusion as `null` is technically not an object but behaves as one in JavaScript.
  - Does not differentiate between different string-like objects (e.g., `new String('foo')` will return `true`, but it is not a primitive string).

### Considerations

When selecting between these approaches, a developer should consider the type of data they are working with and the context of its usage. For type checking with arrays, `Array.isArray()` is preferred due to its specificity and reliability. For general primitive type checks, `typeof` is often employed.

### Library and Features

There are no external libraries referenced in this benchmark, and it primarily tests built-in JavaScript features.

### Alternatives

For checking if a variable is an array, other alternative methods include:

1. **Using `instanceof Array`**: This checks if the variable is an instance of the Array constructor. However, it can yield misleading results when dealing with multiple JavaScript contexts (like iframes) where the Array constructor may differ.

```javascript
   arr instanceof Array
   ```

2. **Checking the constructor**:

```javascript
   arr.constructor === Array
   ```

This is generally less favored due to the pitfalls around inheritance and constructor reassignment.

For checking strings, while `typeof` is common, you might also encounter regular expressions for validating string content, but that's outside the scope of simply determining type.

In summary, the benchmark effectively evaluates the efficiency and reliability of two common methods for type determination in JavaScript, suited for various scenarios in software engineering.

Related benchmarks:

Array.isArray(array) vs. typeof string (version: 1)

Comparing performance of: Array.isArray(arr) vs typeof str === string

Created: one year ago by: Registered User

Jump to the latest result

Array.isArray(arr)

typeof str === string

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):