Benchmark: typeof "undefined" versus falsey check

Script Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
negate

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/124.0.0.0 Safari/537.36

Browser/OS: Chrome 124 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
typeof	6487204.5 Ops/sec
negate	6488988.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what's being tested.

**Benchmark Definition**

The benchmark is testing which approach is faster: using the `typeof` operator or negating the value (using the `!` operator) to check if a value is "falsy" (i.e., undefined, null, 0, empty string, etc.).

**Script Preparation Code**

The script preparation code defines two functions:

* `checkType(val)` returns `true` if `val` is of type `'undefined'`.
* `negate(val)` returns the negation of `val`, effectively checking if it's falsy.

**Html Preparation Code**

There is no HTML preparation code, which means that this benchmark only focuses on JavaScript performance and doesn't involve any DOM-related tasks.

**Individual Test Cases**

The benchmark has two test cases:

1. `typeof`: This test case checks the performance of using the `typeof` operator to check if a value is `'undefined'`.
2. `negate`: This test case checks the performance of negating the value (using the `!` operator) to check if it's falsy.

**Options Compared**

The options being compared are:

* Using `typeof` to check for 'undefined'
* Negating the value (using `!`) to check for falsiness

**Pros and Cons**

Using `typeof`:

Pros:

* More explicit and readable
* Can be used with other operators (e.g., `in`, `instanceof`)

Cons:

* May incur additional overhead due to the function call
* May not be as efficient as a simple negation operation

Negating the value:

Pros:

* Often faster, as it's a single operation
* Can be more concise and readable in some cases

Cons:

* Less explicit and less readable for those unfamiliar with this pattern
* May not work correctly with all types of falsy values (e.g., NaN)

**Library Used**

There is no library used in the provided benchmark code. The `typeof` operator and negation are built-in JavaScript features.

**Special JS Feature or Syntax**

The only special syntax used here is the use of the `!` operator to negate a value, which is a common idiom in JavaScript for checking for falsiness.

**Other Alternatives**

If you're interested in testing other approaches, here are some alternatives:

* Using `Object.prototype.hasOwnProperty.call(obj, 'undefined')`: This approach uses the prototype chain to check if an object has a property called `'undefined'`.
* Using a library like Lodash's `isUndefined` function: This approach relies on a external library for its functionality.
* Using a different negation operator, such as `== -1` or `=== 0`: These approaches use a different syntax to check for falsiness.

Keep in mind that the choice of approach often depends on the specific requirements and constraints of your project.

Related benchmarks:

typeof "undefined" versus falsey check (version: 0)

which is faster

Comparing performance of: typeof vs negate

Created: 3 years ago by: Guest

Jump to the latest result

typeof

negate

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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