Benchmark: isArray vs instanceof vs Symbol.iterator

Script Preparation code:

var types = {
  array: [1,2,3],
  number: 123,
  string: '123',
  map: new Map([[1,1],[2,2],[3,3]]),
  set: new Set([1,2,3]),
  buffer: new ArrayBuffer([1,2,3]),
  boolean: true,
  arrow: () => {},
  function: function () {},
  object: {},
  u8: new Uint8Array(),
  u16: new Uint16Array(),
  u32: new Uint32Array(),
  i8: new Int8Array(),
  i16: new Int16Array(),
  i32: new Int32Array()
}

var keys = Object.keys(types)

Tests:

isArray
keys.map(key => Array.isArray(types[key]) === true)
instanceof
keys.map(key => (types[key] instanceof Array) === true)
Symbol.iterator
keys.map(key => types[key][Symbol.iterator] !== undefined)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
isArray
instanceof
Symbol.iterator

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/127.0.0.0 Safari/537.36

Browser/OS: Chrome 127 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
isArray	689428.9 Ops/sec
instanceof	662279.9 Ops/sec
Symbol.iterator	422943.4 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark tests three different approaches to check if a variable is an array: `isArray`, `instanceof Array`, and `Symbol.iterator`.

**Options Compared**

1. `isArray`: This method uses the built-in `Array.isArray()` function to check if a value is an array.
2. `instanceof Array`: This method checks if an object's prototype chain includes `Array`.
3. `Symbol.iterator`: This method checks if an object has a `Symbol.iterator` property.

**Pros and Cons of Each Approach**

1. **isArray**: Pros:
	* Fast and efficient, as it uses a built-in function.
	* Easy to read and understand.
Cons:
	* May not work correctly for all types of arrays (e.g., TypedArray, Map).
2. **instanceof Array**: Pros:
	* Works correctly for all types of arrays.
Cons:
	* Slower than `isArray` due to the prototype chain lookup.
	* Less readable and maintainable due to its complexity.
3. **Symbol.iterator**: Pros:
	* Fast and efficient, as it only checks if a property exists.
	* More modern and flexible approach.
Cons:
	* Requires JavaScript 10 or later for `Symbol.iterator` support.

**Library Used**

None are used in this benchmark. However, the test cases use `Object.keys()` to iterate over the object properties.

**Special JS Feature/Syntax**

The benchmark uses the `Symbol.iterator` feature, which was introduced in JavaScript 10. This allows objects with a `Symbol.iterator` property to be iterated over using the `for...of` loop or the `Array.from()` method.

**Other Considerations**

* The test cases use an object with various types of arrays and other data structures (e.g., Map, Set, ArrayBuffer) to ensure the tests are comprehensive.
* The benchmark runs on a Chrome browser (127.0.0.0) and provides execution times per second for each test case.

**Alternatives**

If you need to create similar benchmarks, consider using:

1. **Benchmarking libraries**: Such as Benchmark.js or micro-benchmark, which provide more features and flexibility.
2. **Custom testing frameworks**: Like Jest or Mocha, which offer more comprehensive testing capabilities.
3. **JavaScript testing tools**: Such as Jest's `benchmark` package or the `js benchmark` tool, which provide more advanced testing options.

Keep in mind that these alternatives may have different requirements, usage patterns, and performance characteristics compared to MeasureThat.net's simple micro-benchmarking framework.

Related benchmarks:

isArray vs instanceof vs Symbol.iterator (version: 0)

Symbol.iterator also matches TypedArray, Map, and such

Comparing performance of: isArray vs instanceof vs Symbol.iterator

Created: 7 years ago by: Guest

Jump to the latest result

isArray

instanceof

Symbol.iterator

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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