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 };
var obj2 = { a: 1, b: 2, c: 3, e: 5 };

Tests:

undefined
undefined !== obj.d; undefined !== obj2.d;
typeof
'undefined' !== typeof obj.d; 'undefined' !== typeof obj2.d;
in
'd' in obj; 'd' in obj2;
hasOwnProperty
obj.hasOwnProperty( 'd' ); obj2.hasOwnProperty( 'd' );
bool
!! obj.d; !! obj2.d;
hasOwn
Object.hasOwn(obj, 'd'); Object.hasOwn(obj2, '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:

No previous run results

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Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript object lookup performance.

**What is being tested?**

The provided JSON represents a benchmark test case that compares the performance of different ways to check if an object has a certain property. The test case involves two objects, `obj` and `obj2`, with similar properties, but one of them (`obj`) has a specific property missing (`d`).

**What options are compared?**

The individual test cases compare the following five approaches:

1. **Undefined check**: Using the simple equality operator (`===`) to check if a value is `undefined`.
	* Example: `undefined !== obj.d`
2. **Typeof check**: Using the `typeof` operator to check if a property exists and returns an object with that type.
	* Example: `'undefined' !== typeof obj.d`
3. **In operator**: Using the `in` operator to check if a property exists in an object.
	* Example: `'d' in obj`
4. **HasOwnProperty method**: Calling the `hasOwnProperty()` method on an object to check if it has a certain property.
	* Example: `obj.hasOwnProperty('d')`
5. **Boolean coercion**: Using the double-bang operator (`!!`) to coerce a value to a boolean and check if a property exists.
	* Example: `!! obj.d`
6. **Object.hasOwn method**: Calling the `hasOwn()` method on an object (introduced in ES2022) to check if it has a certain property.
	* Example: `Object.hasOwn(obj, 'd')`

**Pros and cons of each approach**

Here's a brief summary:

1. **Undefined check**: Simple and fast, but may return unexpected results if the value is not exactly `undefined`.
	* Pros: Fast
	* Cons: May return incorrect results
2. **Typeof check**: Returns an object type (e.g., `"object"`), which can be useful for debugging.
	* Pros: Returns a specific type; useful for debugging
	* Cons: Returns the type of the value, not just existence
3. **In operator**: Simple and fast, but may return unexpected results if the key is present in the prototype chain.
	* Pros: Fast
	* Cons: May return incorrect results due to prototype chain issues
4. **HasOwnProperty method**: Ensures that the property exists on the object itself (not its prototype chain).
	* Pros: Reliable; returns `true` only if the property exists on the object
	* Cons: Slightly slower than other methods
5. **Boolean coercion**: Coerces a value to boolean, which can lead to unexpected results if not used carefully.
	* Pros: Simple and fast
	* Cons: May return incorrect results due to coercion issues
6. **Object.hasOwn method**: Introduced in ES2022; returns `true` only if the property exists on the object itself (not its prototype chain).
	* Pros: Reliable; returns `true` only if the property exists on the object
	* Cons: May not be supported by older browsers

**Other considerations**

When choosing an approach, consider the following:

* If you need to ensure that a property exists on the object itself (not its prototype chain), use `hasOwnProperty()` or `Object.hasOwn()`.
* If performance is crucial and you're working with modern browsers, use `in` operator.
* Be aware of coercion issues when using boolean coercion (`!!`).
* Avoid relying solely on `typeof`, as it returns the type of the value, not just existence.

**What library is used?**

No specific library is mentioned in this benchmark test case. The code uses native JavaScript methods and operators to perform object lookup performance tests.

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: 3 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

hasOwn

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):