Benchmark: Check if obj.prop is undefined

Script Preparation code:

var obj = { prop: "value" };

Tests:

typeof
return (typeof obj.prop === "undefined")
in
return ("prop" in obj)
== undefined
return (obj.prop === undefined)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
in
== undefined

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2025 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/63.0.3239.84 Chrome/63.0.3239.84 Safari/537.36

Browser/OS: Chromium 63 on Ubuntu

View result in a separate tab

Test name	Executions per second
typeof	16523037.0 Ops/sec
in	15259860.0 Ops/sec
== undefined	5186022.5 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark on MeasureThat.net, which tests the performance of three different approaches to check if an object property is undefined.

**Script Preparation Code and Html Preparation Code**

The script preparation code initializes a variable `obj` with a single property `prop` set to the string value `"value"`. The html preparation code is empty, which means there are no additional HTML elements or scripts being executed before running the benchmark.

**Test Cases**

There are three individual test cases:

1. **typeof**: This test case checks if `obj.prop` has a type of `undefined`.
2. **in**: This test case uses the `in` operator to check if `prop` is present in the object `obj`.
3. **== undefined**: This test case checks for an exact equality with `undefined`.

**Options Compared**

The three test cases compare different approaches to achieve the same result:

* `typeof`: This approach uses the `typeof` operator, which returns a string indicating the type of the variable.
* `in`: This approach uses the `in` operator, which checks if a property is present in an object.
* `== undefined`: This approach uses direct equality comparison with `undefined`.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* `typeof`:
	+ Pros: Simple and concise, widely supported.
	+ Cons: May return a string value other than `"undefined"`, which could be interpreted differently by some browsers or engines.
* `in`:
	+ Pros: More explicit and readable, as it clearly indicates the presence of a property.
	+ Cons: May not work as expected for objects with inherited properties or in certain edge cases.
* `== undefined`:
	+ Pros: Directly checks for an exact equality with `undefined`, which can be more intuitive for some developers.
	+ Cons: May require additional handling to account for cases where the property value is null or a primitive value that might be coerced to `undefined`.

**Library and Special JS Features**

There are no libraries used in this benchmark, nor are any special JavaScript features like async/await, generators, or WebAssembly mentioned. The test cases only use standard JavaScript syntax.

**Other Alternatives**

Alternative approaches could include:

* Using a more explicit check with `obj.hasOwnProperty("prop")` to ensure the property exists before checking its value.
* Utilizing the `Object.is()` method (introduced in ECMAScript 2015) for an exact equality comparison with `undefined`.
* Implementing a custom implementation using bitwise operations or other techniques to optimize performance.

Keep in mind that the choice of approach depends on the specific requirements and constraints of your project.

Related benchmarks:

Check if obj.prop is undefined (version: 2)

Comparing performance of: typeof vs in vs == undefined

Created: 6 years ago by: Registered User

Jump to the latest result

typeof

in

== undefined

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):