Benchmark: typeof undefined vs 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: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Windows

View result in a separate tab

Test name	Executions per second
typeof	12029783.0 Ops/sec
negate	12029484.0 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 and explain what's being tested.

**What is being tested?**

The benchmark measures the performance difference between two approaches to check if a value is "undefined" or not:

1. `typeof` function
2. `!!val` (logical negation) function

In JavaScript, `undefined` is a special value that represents an uninitialized variable, null reference, or missing property. The `typeof` operator returns the type of a value as a string ("undefined", "number", "string", etc.). On the other hand, `!!val` is a shorthand way to check if a value is true (or not false) by converting it to a boolean and then negating the result.

**Options compared**

The two options being compared are:

1. `typeof` function
2. `!!val` (logical negation) function

**Pros and Cons of each approach:**

1. **typeof function**
	* Pros:
		+ Can be used to check for other types as well (e.g., "number", "string", etc.)
		+ Returns a string indicating the type, which can be useful in some cases
	* Cons:
		+ Slower than `!!val` because it involves a function call and a potentially expensive lookup in the `typeof` object
2. **!!val (logical negation)**
	* Pros:
		+ Faster than `typeof` because it's just a simple boolean operation
		+ More concise and easier to read
	* Cons:
		+ Only checks for truthiness, not type
		+ Requires an extra step to negate the result

**Library usage**

There is no library being used in this benchmark. The code snippets provided are self-contained JavaScript functions.

**Special JS features or syntax**

None mentioned.

**Other considerations**

* The `checkType` function is only called with a single argument, which is always `undefined`. This might make the test less representative of real-world scenarios.
* The `negate` function is not actually negating anything; it's just returning the opposite boolean value. If the intention was to negate the result, the function should be modified to use a different approach (e.g., `!!val`).

**Alternatives**

If you wanted to compare other approaches to check if a value is "undefined" or not, here are some alternatives:

1. Use a simple `if` statement: `if (val === undefined) { ... }`
2. Use a conditional expression: `value ? true : false`
3. Use the `==` or `===` operators with a value of 0, as in `if (val == 0 || val === 0) { ... }`

However, since the goal is to measure performance and not just check for "undefined", it's best to stick with the `typeof` function and `!!val` options tested in this benchmark.

Related benchmarks:

typeof undefined vs falsey check (version: 0)

which is faster

Comparing performance of: typeof vs negate

Created: 5 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):