Benchmark: _.isFunction vs typeof

HTML Preparation code:

https://cdn.jsdelivr.net/combine/npm/lodash@4.17.21,npm/lodash@4.17.21/isFunction.min.js

Tests:

_.isFunction
function x() { console.log('xyz'); }; console.log(_.isFunction(x));
typeof
function x() { console.log('xyz'); }; console.log(typeof x === 'function');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
_.isFunction
typeof

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.102 Safari/537.36

Browser/OS: Chrome 98 on Linux

View result in a separate tab

Test name	Executions per second
_.isFunction	168086.2 Ops/sec
typeof	184959.4 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 explain what's being tested.

**Benchmark Definition**

The benchmark is comparing two approaches to check if a function exists: `_.isFunction` (from the Lodash library) and `typeof` (a built-in JavaScript operator).

**Options Compared**

1. **_.isFunction**: This method returns a boolean indicating whether a given value is a function.
2. **typeof**: This operator returns a string describing the type of a variable, which can include "function" if the variable is a function.

**Pros and Cons**

* **_.isFunction**:
	+ Pros: More explicit and readable way to check for functions, less prone to errors due to the string value returned.
	+ Cons: Requires importing the Lodash library, may be slower due to the overhead of a library function call.
* **typeof**:
	+ Pros: Faster and more lightweight, doesn't require importing any libraries.
	+ Cons: Less explicit and readable, can lead to errors if not used correctly (e.g., comparing strings with functions).

**Library - Lodash**

Lodash is a popular utility library for JavaScript that provides various helper functions, including `_.isFunction`. This function returns the first element of an array or null if it's empty. In this benchmark, Lodash is imported and used to check if a function exists.

**Special JS Feature/Syntax**

None mentioned in this specific benchmark.

**Other Considerations**

When using `typeof` to check for functions, be aware that it also returns "object" for constructor functions (e.g., `new Date()`), which might not be desirable behavior. In contrast, `_isFunction` specifically checks if the value is a function.

**Alternatives**

If you don't want to use a library or prefer a more lightweight approach, you can simply use the `typeof` operator and check for "function" in the result string using a regular expression (e.g., `/.^function/.test(typeof x)`). However, this approach may lead to errors if not used correctly.

In general, for most purposes, both approaches are suitable. If readability and explicitness are crucial, `_isFunction` might be a better choice. If speed and lightweight execution are important, `typeof` could be the way to go.

Related benchmarks:

_.isFunction vs typeof (version: 0)

Comparing performance of: _.isFunction vs typeof

Created: 2 years ago by: Guest

Jump to the latest result

_.isFunction

typeof

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):