Benchmark: typeof Undefined vs ===

Script Preparation code:

var a;

Tests:

Type of
if ( typeof a === 'undefined') return
===
if ( a === 'undefined') return

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Type of
===

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark being tested on MeasureThat.net.

**Benchmark Definition**

The benchmark is testing two different approaches for checking if a variable `a` is undefined:

1. Using `typeof a === 'undefined'`
2. Using `a === 'undefined'`

Let's break down each approach:

**Approach 1: `typeof a === 'undefined'`**

This approach uses the `typeof` operator to check the type of `a`. In JavaScript, `typeof` returns one of six values:

* "string"
* "number"
* "boolean"
* "object"
* "function"
* "undefined"

By comparing `a` with `'undefined'`, we're essentially checking if `a` is `undefined`.

Pros:

* This approach is concise and easy to read.
* It's a commonly used pattern in JavaScript.

Cons:

* The comparison can be slower than other approaches, since it involves creating a new string object.
* Some modern browsers may optimize this comparison away in certain situations.

**Approach 2: `a === 'undefined'`**

This approach uses a simple equality check between `a` and the string `'undefined'`.

Pros:

* This approach is often faster than Approach 1, since it only involves a single comparison.
* It's less prone to browser optimizations, which can affect the results.

Cons:

* The code is slightly more verbose than Approach 1.
* Some older browsers may not support this comparison correctly.

**Library Used**

Neither of these approaches relies on any external libraries. However, if we were to use a library for benchmarking or performance testing, some popular options include:

* V8 Benchmark
* Google's Performance Benchmark
* WebKit Benchmarks

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark that would require explanation.

**Other Alternatives**

If you were to rewrite this benchmark using modern JavaScript features, here are some alternatives to consider:

* Using `===` and adding a non-standard `[[Prototype]]` access property: `a === { [[Prototype]]: {} }`
* Using the `is-undefined` function from the `lodash.is undefined` library
* Using a more concise and expressive approach with destructuring: `const { isUndefined } = require('lodash.is undefined'); if (!isUndefined(a))`

However, these alternatives are not directly related to the benchmark being tested on MeasureThat.net.

In summary, this benchmark is testing two different approaches for checking if a variable is undefined in JavaScript. Approach 1 uses `typeof` and has some performance-related considerations, while Approach 2 uses simple equality checks and is generally faster but slightly more verbose.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser/OS: Chrome 69 on Mac OS X 10.14.0

View result in a separate tab

Test name	Executions per second
Type of	13528782.0 Ops/sec
===	13438176.0 Ops/sec

Related benchmarks:

typeof Undefined vs === (version: 0)

Comparing performance of: Type of vs ===

Created: 6 years ago by: Guest

Jump to the latest result

Type of

===

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):