Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty vs. hasOwn

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;
hasOwn
Object.hasOwn(obj, 'd' )

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
hasOwn

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Linux

View result in a separate tab

Test name	Executions per second
undefined	9117480.0 Ops/sec
typeof	23528150.0 Ops/sec
in	23687086.0 Ops/sec
hasOwnProperty	20774578.0 Ops/sec
bool	23202732.0 Ops/sec
hasOwn	8064802.5 Ops/sec

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

LLMs can make mistakes. Check important info.

To understand the benchmark, let's break it down:

**Benchmark Overview**

The benchmark is designed to compare the performance of different ways to access an object property in JavaScript. Specifically, it tests how fast these methods can look up an existing key (or property) within an object.

**Options Compared**

1. `undefined`
2. `typeof`
3. `in`
4. `hasOwnProperty` (which is a method that checks if the object has a specific property)
5. `bool` (which is not explicitly defined in the benchmark; it's likely used to test a boolean expression evaluation)

**Pros and Cons of Each Approach**

1. **undefined**: This approach attempts to access an undefined variable directly. It's unlikely to work as intended, as accessing an undefined variable throws a ReferenceError.
	* Pros: None (it will fail)
	* Cons: Performance is likely to be poor due to the error being thrown
2. `typeof`: This method returns the type of a value (`'object'` for objects). It can be used to access properties by checking if an object has a specific type.
	* Pros: Can be faster than some other methods, as it doesn't require direct property lookup
	* Cons: May not work as expected if the property name is a reserved keyword or starts with a special character
3. `in`: This operator checks if a key exists in an object (using the bracket notation).
	* Pros: Fast and efficient for checking key existence
	* Cons: May be slower than direct property access if the object is very large, as it involves iterating over the object's keys
4. `hasOwnProperty`: This method returns true if the object has the specified property.
	* Pros: Specific to accessing object properties; can be faster than general `in` checks
	* Cons: May not work as expected if the object has a prototype chain with other objects having the same property name
5. `bool`: (Assumed) This test case likely evaluates the boolean value of an expression involving `obj.d`.
	* Pros: Tests the performance of evaluating a simple boolean expression
	* Cons: Not directly related to accessing object properties, which might affect its relevance in this context

**Library Usage**

None mentioned.

**Special JS Features/Syntax**

The benchmark uses some specific JavaScript features and syntax:

1. **Bracket notation (`in`)**: Used to check if a key exists in an object.
2. **Method calls (`hasOwnProperty`, `typeof`)**: These methods are called on objects to access their properties.

**Other Considerations**

When interpreting these results, keep in mind that the test cases may not be directly representative of real-world scenarios, where JavaScript is used for more complex tasks.

As for alternatives:

* Direct property access (e.g., `obj.d`): This approach is likely to be faster than most of the other methods but may require more knowledge about object notation.
* Using a library or framework that provides optimized or standardized ways to access object properties, such as Lodash's `_.has()` function.

The benchmark's focus on basic property lookup can help developers understand how JavaScript's built-in operators and methods handle these scenarios. However, in many real-world applications, more complex use cases require a deeper understanding of JavaScript's features, nuances, and libraries.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty vs. hasOwn (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs hasOwn

Created: 6 months ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

hasOwn

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):