Benchmark: typeof val === "undefined" vs !val vs val === undefined

Script Preparation code:

const undef = undefined
function checkType(val) {
  return typeof val === 'undefined'
}
function negate(val) {
  return !val
}
function equality(val) {
  return val === undefined;
}

Tests:

typeof
const undef = undefined checkType(undef)
negate
const undef = undefined negate(undef)
equality
const undef = undefined equality(undef)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
negate
equality

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what is being tested.

**Benchmark Definition**

The benchmark defines three test cases:

1. `typeof val === "undefined"`: Tests if the result of `typeof` operator on an undefined value is `"undefined"`.
2. `!val`: Tests if the negation of a boolean value using the unary not operator `!` is correct.
3. `val === undefined`: Tests if a loose equality comparison between a value and `undefined` returns true.

The script preparation code defines three functions:

* `checkType(val)`: Returns `true` if `val` is an undefined value.
* `negate(val)`: Returns the negation of `val`.
* `equality(val)`: Returns whether `val` is equal to `undefined`.

**Options Compared**

The benchmark compares three different approaches:

1. Using the `typeof` operator with a loose comparison (`typeof val === "undefined"`).
2. Using the unary not operator for negation (`!val`).
3. Using loose equality comparison (`val === undefined`).

**Pros and Cons of Each Approach**

1. `typeof val === "undefined"`:
	* Pros: More explicit and readable.
	* Cons: May be slower due to string comparison overhead.
2. `!val`:
	* Pros: Faster and more efficient, as it only checks the type of the variable.
	* Cons: Less readable, as the intent is not immediately clear.
3. `val === undefined`:
	* Pros: Fast and efficient, but may be less readable due to the loose comparison.
	* Cons: May return incorrect results for non-primitive values.

**Library Used**

None of the provided benchmark tests use any external libraries.

**Special JS Feature or Syntax**

The benchmark uses a few special JavaScript features:

1. `undefined`: The `undefined` keyword is used to represent an undefined value.
2. `typeof`: The `typeof` operator is used for type checking and equality comparisons.
3. Unary not operator `!`: The unary not operator `!` is used for negation.

The benchmark does not use any other special JavaScript features or syntax that would be considered advanced or esoteric.

**Alternatives**

Other alternatives for testing these types of benchmarks include:

1. Using a library like `assert` to verify expected behavior.
2. Using a testing framework like Jest or Mocha to write and run tests.
3. Implementing the benchmark using C or another low-level language to compare performance with JavaScript.

However, using a microbenchmarking tool like MeasureThat.net provides an efficient way to test specific code snippets and their performance in various browsers and environments.

Related benchmarks:

typeof val === "undefined" vs !val vs val === undefined (version: 0)

Comparing performance of: typeof vs negate vs equality

Created: 3 years ago by: Guest

Jump to the latest result

typeof

negate

equality

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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