Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty vs. Object.prototype.hasOwnProperty.call

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;
Object.prototype.hasOwnProperty.call
Object.prototype.hasOwnProperty.call(obj, 'd')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
Object.prototype.hasOwnProperty.call

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):

LLMs can make mistakes. Check important info.

The provided JSON represents a benchmark test case for measuring the performance of different approaches to checking if a property exists in an object or not. Let's break down what is tested, compared, and their pros and cons:

**What is being tested:**

* Different properties of an object are used to check if they exist:
	+ `undefined` (using the "undefined" value)
	+ `typeof` operator (to check if the property exists as a string)
	+ `in` operator (to check if the property exists in the object's own properties or in its prototype chain)
	+ `hasOwnProperty` method (a custom method that checks if the property exists only in the object's own properties, not in its prototype chain)
	+ `!!` operator (to convert the property value to a boolean using two exclamation marks)

**What is being compared:**

* The performance of each approach is compared by executing them repeatedly and measuring the time taken.

**Approaches and their pros and cons:**

1. **`undefined`**: This approach uses the "undefined" value as a key. It has some limitations:
	+ It's not a typical use case, and it may lead to unexpected behavior.
	+ It relies on the property being `undefined`, which might not always be the case.
2. **`typeof` operator**: This approach uses the `typeof` operator to check if the property exists as a string. Its pros:
	+ It's a standard JavaScript operator, making it easy to understand and use.
	+ However, it can return `object` for primitive values (e.g., numbers or strings), which might not be what you want.
3. **`in` operator**: This approach uses the `in` operator to check if the property exists in the object's own properties or in its prototype chain. Its pros:
	+ It's a standard JavaScript operator, making it easy to understand and use.
	+ However, it can return true for inherited properties, which might not be what you want.
4. **`hasOwnProperty` method**: This approach uses the `hasOwnProperty` method to check if the property exists only in the object's own properties, not in its prototype chain. Its pros:
	+ It's a custom method that provides more control over the lookup process.
	+ However, it might be slower than the other approaches due to the overhead of the method call.
5. **`!!` operator**: This approach uses two exclamation marks to convert the property value to a boolean using the Boolean() function. Its pros:
	+ It's a concise and efficient way to check if the property exists.
	+ However, it relies on the property being converted to a number or string, which might not always be the case.

**Library usage:**

The `hasOwnProperty` method is used from the Object prototype. This method checks if an object has a property of a given name and returns true if found in that particular object's own properties (not its prototype chain), false otherwise.

Other considerations:

* The benchmark uses Chrome 87, which might not be representative for other browsers or versions.
* The test cases use a simple object with only one property (`obj.d`) to simplify the comparison. In real-world scenarios, objects may have more complex structures and properties.
* The benchmark does not account for potential side effects of modifying the `obj` variable during the execution.

**Alternatives:**

Other approaches to checking if a property exists in an object could include:

* Using a custom function or utility library that provides a more efficient or flexible way to perform the lookup.
* Using a different data structure, such as a Set or Map, to store the object's properties and retrieve them efficiently.
* Using a different programming paradigm, such as functional programming, which might provide built-in support for property existence checks.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

Browser/OS: Chrome 87 on Windows

View result in a separate tab

Test name	Executions per second
undefined	4198731.5 Ops/sec
typeof	12401582.0 Ops/sec
in	12267177.0 Ops/sec
hasOwnProperty	10784437.0 Ops/sec
bool	12226467.0 Ops/sec
Object.prototype.hasOwnProperty.call	3882325.0 Ops/sec

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty vs. Object.prototype.hasOwnProperty.call (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs Object.prototype.hasOwnProperty.call

Created: 3 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Object.prototype.hasOwnProperty.call

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):