Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty 222

Script Preparation code:

var obj;

Tests:

undefined
undefined !== obj;
typeof
'undefined' !== typeof obj;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:97.0) Gecko/20100101 Firefox/97.0

Browser/OS: Firefox 97 on Mac OS X 10.14

View result in a separate tab

Test name	Executions per second
undefined	891027264.0 Ops/sec
typeof	880067904.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and analyze what's being tested.

**Benchmark Definition**

The benchmark is designed to measure the performance of object lookup using different methods:

1. `undefined`
2. `typeof`
3. `in`
4. `hasOwnProperty`

These four methods are used to check if a variable (`obj`) is defined or exists in an object.

**Pros and Cons of each approach**

1. **`undefined`**: This method simply checks if the variable is assigned a value (i.e., not undefined). The pros are:
	* Simple and lightweight.
	* Works well for simple cases where `obj` has no properties.
However, the cons are:
	* May be slow due to unnecessary checks.
2. **`typeof`**: This method returns the data type of the variable (`"object"` in this case). The pros are:
	* More informative than just checking for undefined.
	* Works well for cases where `obj` has properties but not all of them have values.
However, the cons are:
	* May be slower due to additional checks and potential string comparison.
3. **`in`**: This method uses the `in` operator to check if a property exists in an object. The pros are:
	* Fast and efficient for most cases.
	* Works well for objects with many properties.
However, the cons are:
	* May not work as expected for objects with inherited properties or complex inheritance trees.
4. **`hasOwnProperty`**: This method checks if a property belongs to the object itself (i.e., not its prototype chain). The pros are:
	* More accurate than `in` for objects with complex inheritance.
	* Works well for cases where you need to check a property's existence without accessing its value.
However, the cons are:
	* May be slower due to additional checks.

**Library: `obj`**

The variable `obj` is assumed to be an object that has properties. The library used is likely built-in JavaScript Object.

**Special JS features or syntax**

There doesn't seem to be any special JavaScript features or syntax used in this benchmark.

**Other alternatives**

Some other methods for checking if a variable exists or has a property include:

* `instanceof`: checks if an object is an instance of a constructor function.
* `Object.prototype.hasOwnProperty.call()`: similar to `hasOwnProperty`, but uses the `call()` method to check if a property belongs to the object itself.
* Using `Set` data structure and adding elements (which would work for this specific benchmark)

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty 222 (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof

Created: 3 years ago by: Guest

Jump to the latest result

undefined

typeof

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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