Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty 3

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;
again
undefined !== obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
again

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON.

**Benchmark Definition:**
The benchmark is testing the performance of different approaches to check if a property exists or has a certain value in an object.

**Test Cases:**

1. `undefined !== obj.d;` - Tests if `obj.d` is undefined.
2. `'undefined' !== typeof obj.d;` - Tests if `typeof obj.d` equals `'undefined'`.
3. `'d' in obj;` - Tests if the property `'d'` exists in `obj`.
4. `obj.hasOwnProperty('d');` - Tests if `obj` has a property named `'d'` using the `hasOwnProperty` method.
5. `!! obj.d;` - Tests if `obj.d` is truthy (i.e., not falsey).
6. `undefined !== obj.d;` (again) - This is essentially a repeat of the first test case.

**Options Compared:**

The benchmark is comparing six different approaches to check for the existence or value of a property in an object:

1. Direct comparison with `undefined`: `obj.d`
2. Comparison with `'undefined'`: `typeof obj.d`
3. Property iteration using `in`: `'d' in obj`
4. Using the `hasOwnProperty` method: `obj.hasOwnProperty('d')`
5. Boolean negation: `!! obj.d`
6. Direct comparison again (for some reason)

**Pros and Cons of Each Approach:**

1. **Direct Comparison with `undefined`**: Simple and efficient, but may not be reliable if the property is set to a non-undefined value.
2. **Comparison with `'undefined'` using `typeof`**: This approach can work on older browsers that don't support `in`. However, it's less intuitive and might lead to incorrect results in some cases.
3. **Property Iteration using `in`**: Fast and reliable, but may not be supported by all browsers (specifically, IE 11).
4. **Using `hasOwnProperty`**: This approach is safe and reliable, especially when working with objects that may have inherited properties from their prototype chain.
5. **Boolean Negation**: Simple and efficient, but might lead to unexpected results if the property is set to a non-truthy value.

**Library and Special JS Features:**
None of the test cases explicitly use any libraries or special JavaScript features beyond the standard language syntax.

**Other Considerations:**

* The benchmark uses `IE 11` as one of the testing browsers, which might be an issue for modern web development.
* Some tests may have different performance characteristics due to caching or other optimizations in modern browsers.
* This benchmark seems to focus on the specific use case of checking property existence and value, rather than a broader set of microbenchmarks.

**Alternative Approaches:**

Other approaches to check for property existence or value might include:

1. Using `Object.hasProperty()` (or `hasOwnProperty` for objects that don't support this method)
2. Utilizing the `getOwnPropertyDescriptor()` method
3. Implementing a custom function using recursion or iteration
4. Leverage modern browser features like `Map.prototype.get()` and `Set.prototype.has()`

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty 3 (version: 0)

Object lookup performance

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

Created: 5 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

again

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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