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: 8 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

bool

199.4M/s

bool with Array

184.3M/s

hasOwnProperty

102.4M/s

View exact numbers

Test name	Executions per second
✓ bool	199,365,168 Ops/sec
bool with Array	184,265,712 Ops/sec
hasOwnProperty	102,402,480 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.

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

Go 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):

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

Go 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):

Related benchmarks

Comparing performance of: `hasOwnProperty vs bool with Array vs bool`