Benchmark: in vs typeof - MeasureThat.net

Script Preparation code:

var a = { test: 1 }

Tests:

in operator
if ('test' in a) return true
typeof
if (typeof a.test !== 'undefined') return true

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
in operator
typeof

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

I'll break down the explanation into smaller sections to make it easier to understand.

**Benchmark Definition and Preparation Code**

The provided JSON represents a JavaScript microbenchmark definition. The benchmark is designed to test two different approaches: using the `in` operator versus using the `typeof` operator with the `===` equality operator.

The preparation code, `var a = { test: 1 }`, creates an object `a` that contains a property named `test` with a value of `1`. This is a common pattern used in benchmarking to provide a simple and consistent starting point for tests.

**Options Compared**

Two options are being compared:

1. **Using the `in` operator**: The `in` operator checks if a property exists in an object.
2. **Using `typeof` with `===`**: This approach uses the `typeof` operator to check if the type of the property is equal to `undefined`, and then checks for the existence of the property.

**Pros and Cons**

Here are some pros and cons of each approach:

* **In Operator**
	+ Pros:
		- Fast and lightweight
		- Works well with objects that have a large number of properties
	+ Cons:
		- May not work as expected with objects that have non-enumerable properties (e.g., `Symbol` properties)
		- May be less readable than other approaches
* **typeof with ===**
	+ Pros:
		- Works well with objects that have a large number of properties
		- Can provide more accurate results for checking property existence
	+ Cons:
		- Slower and more heavyweight compared to the `in` operator
		- May not work as expected if the property has a value other than `undefined`

**Library and Special JS Features**

In this benchmark, there are no libraries used. However, it's worth noting that some JavaScript engines may use internal optimizations or special features that could affect the results of these tests.

**Other Considerations**

When running benchmarks like this one, it's essential to consider factors such as:

* The test data and its distribution
* The browser engine and version being tested
* The hardware platform being used (e.g., CPU architecture, memory size)
* Any additional factors that might affect the results (e.g., caching, JIT optimization)

**Alternatives**

If you're interested in exploring alternative approaches or testing other scenarios, here are some ideas:

* Test using a different data structure, such as an array or a set
* Use a more complex object with multiple levels of nesting
* Try using a library like Lodash to add additional functionality (although this benchmark doesn't use any libraries)
* Experiment with different browser engines or versions
* Investigate the performance characteristics of other operators, such as `===` or `!==`

Keep in mind that microbenchmarks are typically designed to test specific scenarios and optimize for a particular outcome. If you're interested in exploring alternative approaches or testing more complex use cases, it may be helpful to start with smaller benchmarks and gradually increase complexity.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/17.17134

Browser/OS: Edge 17.17134 on Windows

View result in a separate tab

Test name	Executions per second
in operator	11361599.0 Ops/sec
typeof	48315164.0 Ops/sec

Related benchmarks:

in vs typeof (version: 0)

Comparing performance of: in operator vs typeof

Created: 6 years ago by: Guest

Jump to the latest result

in operator

typeof

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):