Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty not

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, 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: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.85 YaBrowser/21.11.3.927 Yowser/2.5 Safari/537.36

Browser/OS: Yandex Browser 21 on Windows

View result in a separate tab

Test name	Executions per second
undefined	3906906.0 Ops/sec
typeof	11293952.0 Ops/sec
in	11121410.0 Ops/sec
hasOwnProperty	10131602.0 Ops/sec
bool	11204776.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The benchmark tests the performance of four different approaches to check if a property exists in an object: `typeof`, `in`, `hasOwnProperty`, and comparing with a boolean value (`!!`).

**Options Compared**

1. **`typeof`**: This approach checks if the result of `typeof` is equal to `'object'`. It's a simple way to check if a variable is an object, but it can be slow for large objects.
2. **`in`**: This approach uses the `in` operator to check if a property exists in the object. It's generally faster than `typeof`, but may not work as expected with certain properties (e.g., function properties).
3. **`hasOwnProperty`**: This approach checks if the property exists by calling the `.hasOwnProperty` method on the object. It's the most reliable way to check for existence, but may be slower due to the method call.
4. **Boolean Comparison (`!!`)**: This approach compares the property value with a boolean value using the double-boolean cast (`!!`). It's fast and simple, but only works if the property value is either `true` or `false`.

**Pros and Cons**

*   **`typeof`**:
    *   Pros: Simple to implement, fast for small objects.
    *   Cons: Slow for large objects, may not work with function properties.
*   **`in`**:
    *   Pros: Generally faster than `typeof`, works well with most properties.
    *   Cons: May not work with function properties, can be slower due to operator overhead.
*   **`hasOwnProperty`**:
    *   Pros: Most reliable way to check for existence, but may be slower.
    *   Cons: Method call overhead can impact performance.
*   **Boolean Comparison (`!!`)**:
    *   Pros: Fast and simple, works well with boolean values.
    *   Cons: Only works for `true` or `false` values.

**Library Usage**

None of the libraries are explicitly mentioned in the benchmark definition. However, if a library is used elsewhere in the code, it might be worth investigating to ensure its impact on performance.

**Special JS Features**

The only special feature present here is the use of double-boolean casting (`!!`) for boolean comparisons. This is a common technique in JavaScript that can be useful when working with boolean values or performing type conversions.

Overall, this benchmark highlights the importance of understanding the trade-offs between different approaches to checking for object property existence in JavaScript.

**Other Alternatives**

Some alternative approaches that might be worth exploring include:

*   Using the `Object.hasOwn` method (introduced in ECMAScript 2020) for a more reliable way to check for existence.
*   Implementing a custom "property lookup" function using a lookup table or other optimization technique.
*   Using a different data structure, such as a Map or Set, instead of an object for property storage.

However, these alternatives might not provide significant performance benefits and should be evaluated on a case-by-case basis.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty not (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>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):