Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty - v2

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d && undefined !== obj.f;
typeof
'undefined' !== typeof obj.d && 'undefined' !== typeof obj.f;
in
'd' in obj && 'f' in obj;
hasOwnProperty
obj.hasOwnProperty('d') && obj.hasOwnProperty('f');
bool
!!obj.d && !!obj.f;

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 dive into the benchmark.

**Benchmark Definition**

The benchmark is designed to measure the performance of different ways to check if a property exists in an object, which is useful in many situations, such as validating user input or checking for undefined values.

**Options Compared**

The benchmark compares five options:

1. `undefined` (using the "is not equal" operator (`!==`) with the object's property)
2. `typeof` (checking the type of the property using the `typeof` operator)
3. `in` (using the "in" operator to check if a property exists in the object)
4. `hasOwnProperty` (a method on objects that returns true if the property is its own, not inherited from another object)
5. A boolean check (`!!obj.d && !!obj.f;`) which uses the double bang operator to coerce the values to booleans

**Pros and Cons of Each Approach**

1. `undefined`:
	* Pros: simple and widely supported
	* Cons: can be slow for large objects or arrays, as it requires searching for the property
2. `typeof`:
	* Pros: generally fast, as it only checks the type of the value
	* Cons: may not work correctly with objects that have custom constructors (e.g., Date)
3. `in`:
	* Pros: fast and efficient, as it uses a hash table lookup
	* Cons: may return true for inherited properties, which can lead to unexpected results
4. `hasOwnProperty`:
	* Pros: precise and reliable, as it only checks the property on the current object
	* Cons: slower than "in" or `typeof`, as it requires method call overhead
5. Boolean check (`!!obj.d && !!obj.f;`):
	* Pros: simple and efficient, as it uses a short-circuit evaluation
	* Cons: may be slower for large objects or arrays, due to the coercion step

**Library Used**

None are explicitly mentioned in the benchmark definition.

**Special JS Features/Syntax**

The only special feature used is the double bang operator (`!!`) which is a common idiom in JavaScript for coercing values to booleans. This is not a specific syntax or feature, but rather an optimization technique.

**Alternatives**

Other alternatives for checking if a property exists in an object include:

* `Object.hasOwn(obj, prop)` (a newer method introduced in ECMAScript 2015)
* `prop in obj` (similar to "in" but uses the `in` operator directly on the property name instead of referencing the object itself)

Note that these alternatives may not be supported by older browsers or environments.

Overall, this benchmark provides a useful comparison of different approaches for checking if a property exists in an object, highlighting the trade-offs between speed, accuracy, and simplicity.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty - v2 (version: 0)

Object lookup performance

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

Created: 3 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):