Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty (Object.create(null))

Script Preparation code:

var obj = Object.assign(Object.create(null), {
    a: 1,
    b: 2,
    c: 3,
    d: 4,
    e: 5
});

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
bool

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
undefined	82348520.0 Ops/sec
typeof	77903920.0 Ops/sec
in	72259888.0 Ops/sec
bool	81941672.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript benchmark test case, measuring the performance of different approaches for object lookup in a specific scenario.

**Benchmark Definition**

The benchmark definition is as follows:

* The script preparation code creates an object `obj` with properties `a` to `e`.
* Each test case compares a different expression:
	+ `undefined`
	+ `typeof`
	+ `in`
	+ `bool`

The expressions are compared against the value of `obj.d`.

**Options Compared**

The benchmark tests four options for comparing an expression against a value:

1. **`undefined`**: Tests if the value is not equal to `undefined`.
2. **`typeof`**: Tests if the type of the value is different from the expected type (in this case, `number`).
3. **`in`**: Tests if the value is present in the object as a property key.
4. **`bool`**: Tests if the value is truthy (i.e., not equal to `0`, `false`, `null`, `undefined`, or an empty string).

**Pros and Cons of Each Approach**

1. **`undefined`**:
	* Pros: Simple, easy to understand, and widely supported.
	* Cons: May be slower due to the need for a separate check for `undefined`.
2. **`typeof`**:
	* Pros: Can handle type checks more efficiently than other approaches.
	* Cons: May not work as expected for certain types (e.g., `NaN`, `Infinity`).
3. **`in`**:
	* Pros: Fast and efficient, especially for large objects.
	* Cons: May not be supported in all browsers or environments (e.g., older versions of Internet Explorer).
4. **`bool`**:
	* Pros: Simple and intuitive, with a clear meaning.
	* Cons: May be slower due to the need for an additional type check.

**Library and Special JS Features**

The benchmark uses no external libraries. It does not use any special JavaScript features beyond what is specified in the benchmark definition.

**Other Considerations**

When choosing an approach for object lookup, consider the following factors:

* **Performance**: If you're dealing with large objects or performance-critical code, `in` might be a good choice.
* **Browser Support**: If you need to support older browsers, make sure to test with those versions.
* **Readability and Maintainability**: Choose an approach that is easy to understand and maintain.

**Alternatives**

Other approaches for object lookup include:

* Using the `===` operator (equal to) instead of `!==`
* Using a `switch` statement or a `case` expression
* Using a library like Lodash's `_.includes()` function

However, these alternatives may not be as efficient or widely supported as the options tested in this benchmark.

Related benchmarks:

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

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs bool

Created: 4 years ago by: Guest

Jump to the latest result

undefined

typeof

in

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):