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

Script Preparation code:

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

Tests:

hasOwnProperty
obj.hasOwnProperty( 'd' );
bool with Array
!! obj['d'];
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
hasOwnProperty
bool with Array
bool

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36

Browser/OS: Chrome 142 on Linux

View result in a separate tab

Test name	Executions per second
hasOwnProperty	102402480.0 Ops/sec
bool with Array	184265712.0 Ops/sec
bool	199365168.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

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

1. `obj.hasOwnProperty('d')`
2. `!! obj['d']` (using array notation)
3. `!! obj.d` (direct property access)

All three approaches are compared to each other.

**Options Compared**

The benchmark is comparing the performance of three different options for checking if a property exists in an object:

* `obj.hasOwnProperty('d')`: This method checks if the object has a property with the specified name. It returns `true` if the property exists, and `false` otherwise.
* `!! obj['d']`: This approach uses double negation (`!!`) to check if the property exists. The `!!` operator is used to convert the boolean result of accessing the property to a number (0 or 1), where 1 represents truthy and 0 represents falsy.
* `!! obj.d`: This approach directly accesses the property using dot notation (`obj.d`). If the property does not exist, this will return `undefined`, which is considered falsy in JavaScript.

**Pros and Cons of Each Approach**

Here's a brief summary of each approach:

* `obj.hasOwnProperty('d')`:
	+ Pros: explicit and safe way to check if a property exists.
	+ Cons: may be slower due to the additional method call.
* `!! obj['d']`:
	+ Pros: concise and efficient, as it avoids the need for an extra method call.
	+ Cons: may be less intuitive or readable for some developers, especially those not familiar with double negation.
* `!! obj.d`:
	+ Pros: simple and direct access to the property.
	+ Cons: assumes that `undefined` is falsy, which may lead to unexpected behavior in certain situations.

**Library Used**

In this benchmark, none of the libraries are explicitly mentioned. However, it's worth noting that JavaScript has a built-in `hasOwnProperty()` method on objects, which can be used for this purpose.

**Special JS Features or Syntax**

None of the test cases use any special JavaScript features or syntax beyond what's standard in modern JavaScript.

**Other Considerations**

When working with object properties, developers should consider factors such as:

* Property existence: Should we check if a property exists before attempting to access it?
* Property presence vs. value: Is it important to distinguish between the existence of a property and its actual value?
* Performance: How do different approaches impact performance in specific use cases?

**Alternatives**

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

* `in`: checks if the property is present in the object's prototype chain.
* `in` + operator (`obj['d'] in obj`): similar to `hasOwnProperty()`, but may be slower due to the extra operation.

However, these alternatives are not included in this benchmark, as they are not explicitly mentioned in the provided code.

Related benchmarks:

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

Object lookup performance

Comparing performance of: hasOwnProperty vs bool with Array vs bool

Created: 8 years ago by: Guest

Jump to the latest result

hasOwnProperty

bool with Array

bool

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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