Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty.call()

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'number' === typeof obj.d;
in
'd' in obj;
hasOwnProperty
hasOwnProperty.call( obj, 'd' );
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark tests the performance of different approaches to check if a property exists in an object:

* `undefined !== obj.d`
* `'number' === typeof obj.d`
* `'d' in obj`
* `hasOwnProperty.call( obj, 'd' )`
* `!! obj.d`

These tests are designed to evaluate the performance of various techniques for checking property existence in objects.

**Options Compared**

The benchmark compares the performance of five different approaches:

1. **`undefined !== obj.d`**: This approach checks if the property exists by comparing its value to `undefined`.
2. **`'number' === typeof obj.d`**: This approach uses the `typeof` operator to check the type of the property.
3. **`'d' in obj`**: This approach uses the `in` operator to check if the property is a key in the object.
4. **`hasOwnProperty.call( obj, 'd' )`**: This approach uses the `hasOwnProperty` method ( inherited from `Object.prototype`) to check if the property exists.
5. **`!! obj.d`**: This approach checks the truthiness of the property using the double bang operator (`!!`).

**Pros and Cons**

Here's a brief analysis of each approach:

1. **`undefined !== obj.d`**:
	* Pros: Simple, widely supported, and fast.
	* Cons: May not work correctly for non-numeric properties or null/undefined values.
2. **`'number' === typeof obj.d`**:
	* Pros: Works for both numeric and string properties, but may be slower due to type checking.
	* Cons: May not work correctly for non-numeric properties or property types other than `string`.
3. **`'d' in obj`**:
	* Pros: Fast, widely supported, and works for any property type.
	* Cons: May return false positives if the object has a property with the same name but different type (e.g., a numeric property named "d").
4. **`hasOwnProperty.call( obj, 'd' )`**:
	* Pros: Works correctly even when `obj` is inherited from another object.
	* Cons: May be slower due to method call overhead.
5. **`!! obj.d`**:
	* Pros: Fast and widely supported, but may not work correctly for null or undefined values.
	* Cons: May return false positives if the property has a value of 0.

**Library Used**

The benchmark uses `Object.prototype.hasOwnProperty`, which is a method inherited from the `Object` prototype. This method checks if an object has a specific property and returns `true` if it does, or `false` otherwise.

**Special JS Feature/Syntax**

None mentioned in this explanation.

**Alternatives**

If you're looking for alternative approaches to check property existence in objects, consider:

* Using the `Object.keys()` method to iterate over an object's own enumerable properties.
* Implementing your own custom function using bitwise operations (e.g., `obj.d === undefined ? 0 : 1`)

Related benchmarks:

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

Object lookup performance

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

Created: 7 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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