Benchmark: jsj 4 undefined vs. typeof vs. in vs. hasOwnProperty

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };
var foo = 'undefined';

Tests:

undefined
undefined === obj.d;
typeof 1
typeof obj.d === 'undefined'
in
!('d' in obj);
hasOwnProperty
!obj.hasOwnProperty( 'd' );
bool
! obj.d;
typeof 2
'undefined' === typeof obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof 1
in
hasOwnProperty
bool
typeof 2

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The provided benchmark tests object lookup performance using four different approaches: `===`, `typeof`, `in`, and `hasOwnProperty`. These approaches are compared to determine which one is the fastest for a given test case.

**Approach 1: Direct Comparison (`===`)**

This approach directly compares the value of `obj.d` with `undefined` using the triple equals operator (`===`). This method is simple and straightforward but may have performance implications due to the comparison operation.

Pros:

* Easy to understand and implement
* Fast execution time (but depends on browser implementation)

Cons:

* May not be as efficient as other approaches in some cases

**Approach 2: Type Checking (`typeof`)**

This approach uses the `typeof` operator to check if `obj.d` is equal to `'undefined'`. This method can be slower than direct comparison because it involves a type check and possibly additional overhead.

Pros:

* More readable code
* Can handle unexpected types or values

Cons:

* May be slower due to type checking
* Not suitable for exact equality checks (e.g., `obj.d === 'undefined'`)

**Approach 3: Membership Test (`in`)**

This approach uses the `in` operator to check if `'d'` is present in the `obj` object. This method can be slower than direct comparison because it involves a lookup operation.

Pros:

* Fast execution time (but depends on browser implementation)
* Suitable for membership tests, not exact equality checks

Cons:

* May return false positives (e.g., if `obj.d` has a different value)

**Approach 4: Property Access (`hasOwnProperty`)**

This approach uses the `hasOwnProperty` method to check if `obj` has a property named `'d'`. This method can be slower than direct comparison because it involves an additional function call.

Pros:

* Suitable for membership tests and handling prototype chains
* Can be more readable code

Cons:

* May be slower due to function call overhead
* Not suitable for exact equality checks (e.g., `obj.d === 'undefined'`)

**Library: None**

There are no external libraries used in this benchmark.

**Special JavaScript Features/Syntax: None**

No special JavaScript features or syntax are used in this benchmark.

Now, let's discuss the test results:

The latest benchmark result shows that the fastest approach for each test case is as follows:

1. `undefined`: Direct Comparison (`===`) (fastest)
2. `typeof 1` and `typeof 2`: Type Checking (`typeof`)
3. `in`: Membership Test (`in`)
4. `hasOwnProperty`: Property Access (`hasOwnProperty`)
5. `bool`: Direct Comparison (`===`) (fastest)

**Other Alternatives**

If you want to explore other approaches or test different scenarios, here are some alternatives:

* Use a loop-based approach to iterate over the object's properties and compare with `'undefined'`.
* Test exact equality checks using `obj.d === 'undefined'` instead of `obj.d === undefined`.
* Try using alternative membership tests like `Object.prototype.hasOwnProperty.call(obj, 'd')`.
* Experiment with different browsers or platforms to see if performance varies.

Keep in mind that these alternatives may not be as straightforward to implement or understand as the original benchmark.

Related benchmarks:

jsj 4 undefined vs. typeof vs. in vs. hasOwnProperty (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof 1 vs in vs hasOwnProperty vs bool vs typeof 2

Created: 7 years ago by: Guest

Jump to the latest result

undefined

typeof 1

in

hasOwnProperty

bool

typeof 2

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):