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

Script Preparation code:

var hasOwnProperty = Object.prototype.hasOwnProperty;
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
hasOwnProperty.call( obj, '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

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its various components.

**Benchmark Definition**

The benchmark is defined by two JSON objects: `Benchmark Definition` and `Individual test cases`.

*   The `Benchmark Definition` specifies the general scope of the benchmark, which in this case is "Object lookup performance".
*   The `Individual test cases` define specific sub-benchmarks that are run to measure performance. Each sub-benchmark has a unique name, and its purpose is to test the performance of different approaches for object lookup.

**Options Compared**

The options being compared are:

1.  **`undefined`**: This option tests the performance of using `undefined` as a comparison value.
2.  **`typeof`**: This option tests the performance of using the `typeof` operator to determine if a variable is `undefined`.
3.  **`in`**: This option tests the performance of using the `in` operator to check if a property exists in an object.
4.  **`hasOwnProperty`**: This option tests the performance of using the `hasOwnProperty` method to check if a property exists in an object.
5.  **`bool`**: This option tests the performance of converting a boolean value to `true` or `false`, which is equivalent to checking for `undefined` but uses a more straightforward approach.

**Pros and Cons**

Here's a brief overview of each option:

*   **`undefined`**: This option is simple and straightforward. It checks if the variable is equal to `undefined`. However, it may not be the most efficient or reliable way to check for `undefined`, as it can lead to unexpected results in certain scenarios.
    *   Pros: Simple, straightforward.
    *   Cons: May not be efficient or reliable.
*   **`typeof`**: This option uses the `typeof` operator to determine if a variable is `undefined`. While this approach provides more robust results than using `undefined`, it may still incur additional overhead due to the complexity of the operator.
    *   Pros: More robust and reliable than `undefined`.
    *   Cons: May incur additional overhead.
*   **`in`**: This option uses the `in` operator to check if a property exists in an object. While this approach is efficient, it only checks for existing properties and may not cover all cases where checking for `undefined` is necessary.
    *   Pros: Efficient and covers some cases.
    *   Cons: May not cover all cases where checking for `undefined` is necessary.
*   **`hasOwnProperty`**: This option uses the `hasOwnProperty` method to check if a property exists in an object. While this approach provides more robust results than using `in`, it may still incur additional overhead due to the complexity of the method.
    *   Pros: More robust and reliable than `in`.
    *   Cons: May incur additional overhead.
*   **`bool`**: This option tests the performance of converting a boolean value to `true` or `false`. While this approach provides a straightforward way to check for `undefined`, it may not be as efficient as other approaches, especially if the conversion is performed frequently.

**Libraries and Features**

The test case uses no external libraries. However, it does use built-in JavaScript features like the `in` operator and the `hasOwnProperty` method.

If you wanted to include a library or feature to make this benchmark more specific, here are some suggestions:

*   **Use a testing library**: Consider using a testing library like Jest or Mocha to make the benchmarking process easier and more robust.
*   **Include additional features**: You could consider adding additional features like support for different data types (e.g., numbers, strings) or use cases that cover more edge cases.

**Other Alternatives**

Here are some other alternatives you could consider:

1.  Use a different comparison operator: Instead of using `in` or `hasOwnProperty`, you could try using the `===` operator to check for equality.
2.  Test performance with different data sizes: You could test the performance of each option with different data sizes to see how they scale.
3.  Compare with other languages: You could consider benchmarking these options in other programming languages to see if there are any significant differences.

Overall, this benchmark provides a good starting point for understanding the performance characteristics of different approaches for object lookup in JavaScript. By exploring the pros and cons of each option, you can make informed decisions about which approach is best suited for your specific use case.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser/OS: Chrome 69 on Windows

View result in a separate tab

Test name	Executions per second
undefined	3252326.5 Ops/sec
typeof	9773020.0 Ops/sec
in	8927788.0 Ops/sec
hasOwnProperty	4524568.0 Ops/sec
bool	9799933.0 Ops/sec

Related benchmarks:

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

Object lookup performance

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

Created: 6 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 26 days ago):