Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty 23

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( '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:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Browser/OS: Chrome 78 on Windows

View result in a separate tab

Test name	Executions per second
undefined	3356374.8 Ops/sec
typeof	9588987.0 Ops/sec
in	9567423.0 Ops/sec
hasOwnProperty	8476085.0 Ops/sec
bool	9606151.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks and explore what's being tested on MeasureThat.net.

**Benchmark Definition**

The benchmark is designed to measure the performance of object lookup using different methods: `undefined`, `typeof`, `in`, and `hasOwnProperty`. The benchmark consists of five individual test cases, each evaluating a specific expression:

1. `undefined !== obj.d;`
2. `'undefined' !== typeof obj.d;`
3. `'d' in obj;`
4. `obj.hasOwnProperty('d');`
5. `! obj.d;`

**Options Compared**

The benchmark is comparing the performance of these five options for object lookup. The options are:

* `undefined` (using the literal value "undefined")
* `typeof` (checking if the property exists using the `typeof` operator)
* `in` (checking if a property exists using the `in` operator)
* `hasOwnProperty` (checking if an object has a specific property using the `hasOwnProperty` method)
* `bool` (using the logical NOT operator (`!`) to check for falsy values)

**Pros and Cons**

Here's a brief summary of each option:

* **Undefined**: This is the most straightforward approach, but it can be slow because JavaScript has to perform a lookup in the object prototype chain.
* **typeof**: This method checks if the property exists in the object's own properties or in its prototype chain. It's faster than `undefined` but may incur additional overhead due to the `typeof` operator.
* **in**: The `in` operator is optimized for performance and can be faster than `typeof`. However, it only checks if the property exists in the object's own properties, not in its prototype chain.
* **hasOwnProperty**: This method specifically checks if an object has a specific property without looking up the prototype chain. It's the most efficient way to check for existence, but it may not be available on all objects (e.g., non-object values).
* **Bool**: Using the logical NOT operator (`!`) to check for falsy values is not an object lookup method per se. This option is likely used to compare with the other methods.

**Library and Purpose**

None of the options require a specific library, but `hasOwnProperty` is often used in conjunction with other object-related libraries or methods (e.g., when working with DOM elements).

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax used in this benchmark. The focus is on comparing different object lookup methods.

**Other Alternatives**

If you're looking for alternative approaches to object lookup, consider the following:

* Using `Object.prototype.hasOwnProperty.call(obj, 'd')` (an older way of using `hasOwnProperty`)
* Using a library like Lodash's `isPlainObject` function
* Implementing your own custom lookup method using bitwise operations or regex

Keep in mind that these alternatives may not be as efficient or straightforward to use as the methods tested in this benchmark.

I hope this explanation helps you understand what's being tested on MeasureThat.net!

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty 23 (version: 0)

Object lookup performance

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

Created: 4 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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