Benchmark: Testing for false vs === undefined vs hasOwnProperty vs in for undefined member

Tests:

test truth
var n = {}; while(true) { if(!n.foo) break; }
test undefined
var n = {}; while(true) { if(n.foo===undefined) break; }
test hasOwnProperty
var n = {}; while(true) { if(!n.hasOwnProperty('foo')) break; }
test in ===
var n = {}; while(true) { if('foo' in n === false) break; }
test in !
var n = {}; while(true) { if(!('foo' in n)) break; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
test truth
test undefined
test hasOwnProperty
test in ===
test in !

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated one month ago):

LLMs can make mistakes. Check important info.

This benchmark investigates the performance of different ways to check if a property exists in an object in JavaScript:

* **`!n.foo` (Test Name: `test truth`)**: This uses a simple logical negation (`!`). If the property `foo` doesn't exist on the object `n`, accessing it will return `undefined`.  The exclamation mark negates this, resulting in `true`.
* **`n.foo === undefined` (Test Name: `test undefined`)**: This explicitly compares the value of `n.foo` to `undefined` using strict equality (`===`).

* **`!n.hasOwnProperty('foo')` (Test Name: `test hasOwnProperty`)**: This utilizes the built-in `hasOwnProperty()` method, which directly checks if a property is owned by the object itself. It returns `false` for non-existent properties and `true` otherwise.
* **`'foo' in n === false` (Test Name: `test in ===")`.**  This uses the `in` operator to check if `foo` is a property of `n`. The result is compared with `false` using strict equality (`===`).

Let's break down the pros and cons:

* **`!n.foo`**:
    * **Pro:** Concise and easy to read.
    * **Con:** Can be less performant than other options due to potential extra checks involved in accessing properties that don't exist.
* **`n.foo === undefined`**:
    * **Pro:**  Clear and explicit comparison.
    * **Con:**  Can be slightly slower than `hasOwnProperty()` for large objects due to the strict equality check.

* **`!n.hasOwnProperty('foo')`**:
    * **Pro:** Considered the most performant option as it's designed to directly check property ownership. Often used in best practices.
    * **Con:** Slightly more verbose than other options.

*  **`'foo' in n === false`**:
    * **Pro:** Readable and similar in logic to `!n.hasOwnProperty('foo')`. 
    * **Con:** Potentially less performant than `hasOwnProperty()` depending on JavaScript engine implementations.

**Alternatives:**

While the benchmark focuses on these methods, other techniques exist:

* **Object Property Existence Checkers (e.g., lodash):** Libraries like Lodash offer optimized functions for checking property existence (`_.has`, `_.get`).
* **Early Returns:** If you have a complex conditional flow involving property checks, consider using early return statements to optimize performance based on immediate conditions.

Let me know if you have any more questions or need further clarification!

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser/OS: Chrome 108 on Windows

View result in a separate tab

Test name	Executions per second
test truth	1078204800.0 Ops/sec
test undefined	12296229.0 Ops/sec
test hasOwnProperty	160367280.0 Ops/sec
test in ===	1127436672.0 Ops/sec
test in !	1126103936.0 Ops/sec

Related benchmarks:

Testing for false vs === undefined vs hasOwnProperty vs in for undefined member (version: 0)

Is there a performance benefit to replacing === undefined with a logical test?

Comparing performance of: test truth vs test undefined vs test hasOwnProperty vs test in === vs test in !

Created: one year ago by: Guest

Jump to the latest result

test truth

test undefined

test hasOwnProperty

test in ===

test in !

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated one month ago):