Benchmark: typeof first or second

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

typeof first
typeof obj.d !== 'undefined'
typeof second
'undefined' !== typeof obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof first
typeof second

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested, compared, and what are the pros and cons of each approach.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark that tests the performance of two different ways to check if a value is defined or not. The benchmark is designed to measure the performance of `typeof` operator with both approaches:

1. `typeof first`
2. `'undefined' !== typeof second`

**What are the options being compared?**

The two options being compared are:

1. Using the `typeof` operator with a variable (`first`) as its argument.
2. Using the strict equality operator (`'undefined' !==`) with a variable (`second`) as its operand.

**Pros and Cons of each approach:**

1. **Using the `typeof` operator with a variable (`first`):**
	* Pros:
		+ Easy to read and write
		+ Intuitive for developers who are familiar with the `typeof` operator
	* Cons:
		+ May be slower due to the overhead of function calls (e.g., `typeof` is a built-in function)
		+ Can lead to unexpected behavior if not used carefully (e.g., `typeof null` returns `'object'`)
2. **Using the strict equality operator (`'undefined' !==`) with a variable (`second`):**
	* Pros:
		+ May be faster due to its simplicity and lack of function call overhead
		+ More explicit and safe for checking undefined values (e.g., `x === undefined` will return `false` instead of `'undefined' !== x`)
	* Cons:
		+ Less intuitive for developers who are not familiar with this syntax
		+ May require additional null checks to avoid false positives

**Library and special JS features:**

The benchmark does not use any external libraries, but it assumes that the `typeof` operator is available and implemented correctly by the JavaScript engine.

There are no special JS features used in this benchmark.

**Other alternatives:**

If you wanted to test alternative approaches for checking if a value is defined or not, some possible options could be:

* Using `hasOwnProperty()` on an object to check if a property exists (e.g., `obj.hasOwnProperty('property')`)
* Using `in` operator to check if a variable is in the global scope (e.g., `x in global`)
* Using a custom function or utility library for checking undefined values

However, these alternatives would likely have different performance characteristics and may not be as straightforward to use as the two options being compared.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Linux; Android 9; Nokia 8 Sirocco) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.90 Mobile Safari/537.36

Browser/OS: Chrome Mobile 73 on Android

View result in a separate tab

Test name	Executions per second
typeof first	5356307.5 Ops/sec
typeof second	5368219.0 Ops/sec

Related benchmarks:

typeof first or second (version: 0)

Object lookup performance

Comparing performance of: typeof first vs typeof second

Created: 5 years ago by: Guest

Jump to the latest result

typeof first

typeof second

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):