Benchmark: void 0 vs undefined vs variable containing undefined

Script Preparation code:

var a = 1, u = void 0;

Tests:

undefined
if(a===undefined)console.log(a);
void 0
if(a===void 0)console.log(a);
constant containing undefined
if(a===u)console.log(a);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
void 0
constant containing undefined

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_5 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.5 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 15 on iOS 15.5

View result in a separate tab

Test name	Executions per second
undefined	8393813.0 Ops/sec
void 0	20734222.0 Ops/sec
constant containing undefined	12156584.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its various components.

**Benchmark Definition JSON**

The `Benchmark Definition` is a simple JavaScript expression that tests whether three different values are equal to `a`, which is initialized with the value `1`. The expressions are:

1. `if(a===undefined)console.log(a);`
2. `if(a===void 0)console.log(a);`
3. `if(a===u)console.log(a);`

Here, `void 0` and `undefined` are both used to represent the absence of a value, while `u` is a variable containing `undefined`. The `===` operator checks for strict equality between two values.

**Options Compared**

The three options being compared are:

1. `undefined`
2. `void 0` (which is equivalent to `undefined`)
3. A variable `u` that contains the value `undefined`

These options represent different ways of checking whether a value is absent or null.

**Pros and Cons of Each Approach**

1. **Undefined**: The simplest way to check for an absent value, but it's not always clear what this means in the context of JavaScript. Some developers might interpret it as "not present" while others see it as "null-like behavior".
2. **Void 0**: This is a standard convention in JavaScript that indicates the absence of a value. However, some older browsers or versions of Internet Explorer (IE) may not support `void 0`. Additionally, modern browsers like Safari and Chrome might use `undefined` instead.
3. **Variable containing undefined**: Using a variable to represent an absent value can be confusing, especially for developers unfamiliar with JavaScript's nuances.

**Library and Purpose**

In this benchmark, there is no explicit library used. The expressions rely on built-in JavaScript features, such as the `===` operator and variables.

**Special JS Feature or Syntax**

None mentioned in the provided information.

**Other Alternatives**

While not explicitly mentioned in the benchmark, alternative approaches to checking for absent values could include:

* Using a specific check like `if (a == null) console.log(a);`
* Utilizing `hasOwnProperty` with an object, as in `if (!u.hasOwnProperty('')) console.log(u);`
* Employing more advanced techniques like using the `Object.is()` method or `===` with an explicit type coercion

However, these alternatives are not being tested or compared in this specific benchmark.

The provided benchmark offers a simple and straightforward way to compare how different browsers (or versions) handle absent values in JavaScript.

Related benchmarks:

void 0 vs undefined vs variable containing undefined (version: 0)

Comparing performance of: undefined vs void 0 vs constant containing undefined

Created: 11 months ago by: Registered User

Jump to the latest result

undefined

void 0

constant containing undefined

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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