Benchmark: undefined vs. typeof vs. in vs. hasOwnPropertyjjj

Script Preparation code:

var obj = { a: 1, b: 2, c: 3,   e: 5 };

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( '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

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Windows

View result in a separate tab

Test name	Executions per second
undefined	7440731.0 Ops/sec
typeof	20021340.0 Ops/sec
in	20244816.0 Ops/sec
hasOwnProperty	18133332.0 Ops/sec
bool	19194742.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and explain what's being tested, compared, and the pros and cons of each approach.

**Benchmark Overview**

The benchmark measures the performance of different JavaScript operators for object lookup:

* `undefined`
* `typeof` (to check if a property is defined)
* `in` (to check if a property exists in an object)
* `hasOwnProperty` (a method that checks if an object has a property with the given name)
* `!!` (a conditional operator to convert a value to a boolean)

The benchmark uses a single test case object, `obj`, which is defined as `{ a: 1, b: 2, c: 3, e: 5 }`.

**Operators Comparison**

Here's what each operator is doing:

* `undefined`: Checks if the property `d` does not exist in the object. In this case, since `d` is not present, it will return `true`.
* `typeof obj.d`: Checks the type of the property `d` in the object. Since `d` is a string (the value "5"), it will return `"string"`. This operator is actually checking if `d` is defined and has a certain type, not just exists.
* `in`: Checks if the property `d` exists in the object using the `in` operator. This will return `false`, since `d` does not exist.
* `hasOwnProperty obj.d`: Similar to `in`, but this method specifically checks if the property `d` is an own property of the object, meaning it's not inherited from a parent object. This will also return `false`.
* `!! obj.d`: Converts the value of `obj.d` to a boolean using the double bang operator (`!!`). Since `obj.d` is the string "5", this will return `true`, because any non-empty string is considered truthy in JavaScript.

**Performance Comparison**

The benchmark measures the performance (in executions per second) of each operator. The results show that:

* `in` and `hasOwnProperty` are very fast, indicating they're optimized for object lookup.
* `typeof` is slower than `in` and `hasOwnProperty`, likely due to its additional checks for property type and existence.
* `!! obj.d` is faster than the other operators, possibly because it's a simple boolean conversion.

**Pros and Cons**

Here are some pros and cons of each approach:

* `undefined`: Fast but might be optimized by the browser for cases where `d` doesn't exist. However, this can lead to unexpected behavior if used incorrectly.
* `typeof`: May be slower due to additional checks, but is more flexible and allows checking property types. Might not be suitable for all use cases.
* `in`: Very fast and optimized for object lookup. Suitable for most cases where you need to check if a property exists in an object.
* `hasOwnProperty`: Similar to `in`, but specifically checks own properties. Can be slower due to the additional check, but is more precise when dealing with inheritance.
* `!! obj.d`: Simple and fast boolean conversion. Might not be suitable for all use cases, as it assumes a non-empty string is truthy.

**Other Considerations**

Keep in mind that JavaScript engines may optimize certain operators or methods differently across browsers and versions. Additionally, the performance results might vary depending on the specific test case object, its size, and complexity.

Some alternative approaches to consider:

* Using `Object.hasOwn(obj, 'd')` instead of `hasOwnProperty`, which is a more modern method for checking if an object has a property with a given name.
* Using `obj.d in obj` instead of `in`, which can be slightly faster due to the shorter syntax.
* Avoiding the use of `typeof` or `!!` for simple boolean conversions, as they might not be necessary and add extra overhead.

Please note that these alternatives are not necessarily better or worse than the original operators; they just offer different trade-offs and may suit specific use cases better.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnPropertyjjj (version: 0)

Object lookup performance

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

Created: 11 months 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 2 months ago):