Benchmark: typeof vs undefined

Script Preparation code:

var x;
var und = 'unde';
und += 'fined'

Tests:

typeof str
typeof x==='undefined'
typeof var
typeof x === und;
real undefined
x === undefined

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof str
typeof var
real undefined

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.4 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 15 on iOS 15.4.1

View result in a separate tab

Test name	Executions per second
typeof str	25103182.0 Ops/sec
typeof var	13027119.0 Ops/sec
real undefined	8744002.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its options.

**Benchmark Overview**

The test case measures the performance of JavaScript's `typeof` operator, which returns a string describing the type of a variable or value. The test compares three different scenarios:

1. **`typeof x === 'undefined'`**: This checks if the variable `x` is undefined.
2. **`typeof x === und`**: Where `und` is a string literal `'unde'`. This checks if `x` has type `string`.
3. **`x === undefined`**: This directly compares the value of `x` with `undefined`.

**Options Compared**

The test case compares three different options:

1. **`typeof x === 'undefined'`**: Uses the `typeof` operator to check the type of `x`. This is a straightforward way to check if `x` is undefined.
2. **`typeof x === und`**: Uses the `typeof` operator to check the type of `x`, but with a custom string literal `'unde'`.
3. **`x === undefined`**: Directly compares the value of `x` with `undefined`.

**Pros and Cons**

Here are some pros and cons of each option:

1. **`typeof x === 'undefined'`**:
	* Pros: Simple, easy to read.
	* Cons: May be slower due to string comparison, which is not necessary for checking if a value is undefined.
2. **`typeof x === und`**:
	* Pros: Can be faster than the first option since it avoids unnecessary string comparison.
	* Cons: Requires a custom string literal `'unde'`, which may make the code harder to read and maintain.
3. **`x === undefined`**:
	* Pros: Directly compares the value with `undefined`, no need for type checking.
	* Cons: May be slower due to direct comparison, which can be optimized by the JavaScript engine.

**Library/Feature**

There is no specific library mentioned in the benchmark definition or test cases. The `typeof` operator is a built-in JavaScript operator.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark. It only uses standard JavaScript syntax and operators.

**Alternatives**

Some alternative approaches to measure the performance of `typeof` could be:

1. Measuring the performance of `x === undefined` directly, without using `typeof`.
2. Using a library like `fast-check` which provides faster ways to check types.
3. Implementing a custom type checker using JavaScript's `Object.prototype.toString()` method.

However, these alternatives would require significant changes to the benchmark code and may not be as straightforward or representative of real-world usage scenarios.

Related benchmarks:

typeof vs undefined (version: 0)

Comparing performance of: typeof str vs typeof var vs real undefined

Created: 4 years ago by: Registered User

Jump to the latest result

typeof str

typeof var

real undefined

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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