Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty vs non strict

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;
non strict equal
obj.d != null

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
non strict equal

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 14_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.3 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 14 on iOS 14.4

View result in a separate tab

Test name	Executions per second
undefined	5415998.5 Ops/sec
typeof	15605341.0 Ops/sec
in	15819007.0 Ops/sec
hasOwnProperty	15242405.0 Ops/sec
bool	15443088.0 Ops/sec
non strict equal	15215307.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark definition represents the test case being run. In this case, the test is object lookup performance, and it compares six different approaches:

1. `undefined`
2. `typeof` (checking if a variable is an object or not)
3. `in` (a boolean expression using the `in` operator)
4. `hasOwnProperty` (a method to check if an object has a property with a given name)
5. `!!` (a boolean conversion operator, which converts its operand to a boolean value) - Note: This test actually uses `bool`, not `!!`. I'll explain the difference later.
6. `non strict equal` (a non-strict equality check using `!= null`)

**Options Compared**

The options compared are:

* `undefined`: Using the literal value `undefined`
* `typeof`: Checking if an object exists, but not its type
* `in`: A boolean expression that checks for property existence
* `hasOwnProperty`: A method to check if an object has a property with a given name
* `!!` (or `bool`, as mentioned earlier): A boolean conversion operator

**Pros and Cons of Each Approach**

1. **Undefined**: This approach is simple and straightforward but may not be the most efficient way to check for undefined values, especially in modern JavaScript environments.
2. **typeof**: Checking if an object exists can lead to unexpected results if the variable has been deleted or is a host object (e.g., `undefined`). However, it's often faster than using `in` or `hasOwnProperty`.
3. **In**: The `in` operator checks for property existence and returns a boolean value. It can be slower than using `typeof`, especially for large objects.
4. **HasOwnProperty**: This method is specific to objects and checks if the object has a property with a given name. While it's slower than `typeof`, it provides more accurate results, as it doesn't return false positives like `in` might.
5. **!!** (or `bool`): This conversion operator converts its operand to a boolean value. It's fast and efficient but may not provide the same level of accuracy as using `hasOwnProperty`.

**Special JS Feature or Syntax**

The test uses special JavaScript features:

* The `!!` operator is used, which converts its operand to a boolean value.
* The `bool` variable is declared, which holds the result of the conversion (in this case, `false`, since `obj.d` is not null).
* The `hasOwnProperty` method is used to check if an object has a property with a given name.

**Other Alternatives**

If you need to perform object lookup checks in JavaScript, other alternatives include:

* Using the `Object.prototype.hasOwnProperty.call()` method (which is similar to `hasOwnProperty`, but can be called on any object)
* Using a simple `if` statement or conditional expression to check for undefined values
* Using the `===` operator (strict equality) and checking if both sides are not null

Keep in mind that performance differences between these approaches may vary depending on your specific use case, JavaScript environment, and hardware.

For this particular benchmark, MeasureThat.net is comparing the performance of different object lookup approaches to determine which one is the fastest.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty vs non strict (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs non strict equal

Created: 3 years ago by: Registered User

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

non strict equal

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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