Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty vs bool vs Object.hasOwn

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5, f:6, g:7 };

Tests:

undefined
obj.d !== undefined;
typeof
typeof obj.d !== 'undefined';
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;
Object.hasOwn
Object.hasOwn(obj, 'd')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
Object.hasOwn

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark measures the performance of different JavaScript operators when used to check if a property exists or has a certain value in an object. The comparison is made between:

1. `undefined` (using `obj.d !== undefined`)
2. `typeof` (checking if `obj.d` has a certain type, e.g., number)
3. `in` (using the `in` operator to check if a property exists)
4. `hasOwnProperty` (using the `hasOwnProperty` method to check if a property is owned by the object)
5. `bool` (using a boolean cast (`!! obj.d`) to check if a value is truthy or falsy)
6. `Object.hasOwn` (using the `Object.hasOwn` method to check if an object has a certain property)

**Library and Purpose**

* `hasOwnProperty`: A built-in JavaScript method that checks if an object has a certain property as its own property, rather than inheriting it from its prototype chain.

**Special JS Feature or Syntax**

None of the benchmark cases use any special JavaScript features or syntax, such as async/await, promises, or arrow functions. All comparisons are made using standard JavaScript operators and methods.

**Options Compared**

The benchmark compares the performance of each operator in different contexts:

1. Checking if a property exists (`in` vs `hasOwnProperty`)
2. Checking if a value is truthy or falsy (`bool` vs other approaches)
3. Using `typeof` to check the type of a property

**Pros and Cons of Different Approaches**

Here's a brief overview of each approach:

1. **`in` operator**: Pros: Simple, fast, and widely supported. Cons: May not work as expected in some cases (e.g., when using `in` with `Object.prototype`), and its behavior can be nuanced.
2. **`hasOwnProperty` method**: Pros: More precise control over the check, especially when dealing with inherited properties. Cons: Method call overhead and potential performance impact.
3. **Boolean casting (`!! obj.d`)**: Pros: Simple, fast, and widely supported (though it may not work as expected if `obj.d` is a negative number). Cons: May be less intuitive than other approaches, and its behavior can be nuanced.
4. **`typeof` operator**: Pros: Fast and accurate for checking type, but may not work well with complex types or objects. Cons: Less intuitive and potentially more error-prone.

**Other Alternatives**

If the `in` operator is too slow or unpredictable, other alternatives could include:

1. `Object.keys(obj).includes('d')`: This method uses the `keys()` method to get an array of property names and then checks if `'d'` is included.
2. `obj['d'] !== undefined`: This approach uses the bracket notation to access the property directly, which may be faster but also more brittle.

However, these alternatives may have different performance characteristics or trade-offs in terms of simplicity and accuracy.

Keep in mind that the specific choice of operator depends on the use case and requirements. The benchmark results should provide a general indication of each approach's relative performance.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36

Browser/OS: Chrome 106 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
undefined	5589580.0 Ops/sec
typeof	15310189.0 Ops/sec
in	15162712.0 Ops/sec
hasOwnProperty	12743463.0 Ops/sec
bool	15367553.0 Ops/sec
Object.hasOwn	4986365.0 Ops/sec

Related benchmarks:

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

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs Object.hasOwn

Created: 2 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Object.hasOwn

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):