Benchmark: undefined vs. typeof vs. in vs. operator

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;
operator
obj.d >= 0;
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
operator
bool

Fastest: N/A

Slowest: N/A

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.

**Benchmark Definition JSON**

The provided JSON represents a benchmark test that measures the performance of different JavaScript operators: `undefined`, `typeof`, `in`, and `operator`. The test also includes a "bool" operator, which is likely used to check if a value is truthy or not. Here's what each operator does:

1. **`undefined`**: Returns `true` if the variable is undefined.
2. **`typeof`**: Returns the data type of the variable (e.g., "number", "string", etc.).
3. **`in`**: Checks if a property exists in an object using the dot notation (`obj.propertyName`). It returns `true` if the property exists and `false` otherwise.
4. **`operator`**: This operator is not explicitly defined, but based on the benchmark code, it's likely used to check if a value is greater than or equal to 0.

**Options Compared**

The test compares the performance of each operator in different scenarios:

* Using an undefined variable (`undefined`)
* Using a reference to a property that exists in the object (`obj.d`)
* Using a string literal (`'d'`) as the property name
* Checking if a value is greater than or equal to 0 using the `>=` operator

**Pros and Cons of Different Approaches**

Here's a brief analysis of each approach:

1. **`undefined`**: This operator is likely to be faster since it involves a simple check against an undefined variable. However, its performance may vary depending on the specific use case.
2. **`typeof`**: Using `typeof` can be slower than checking for existence using `in`, as it performs additional type checks. On the other hand, `typeof` provides more information about the value's data type.
3. **`in`**: Checking for property existence using `in` is generally faster since it only requires a single operation to check if the property exists in the object. However, it may not be as readable or intuitive as using dot notation.
4. **`operator`**: The performance of this operator depends on the specific use case and the value being compared. In general, using a numerical comparison (`>=`) is likely to be faster than using a string comparison.

**Library Usage**

There are no notable libraries used in this benchmark. However, some optimizations might be applied at a lower level using browser-specific features or WebAssembly.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax used in this benchmark. The code is straightforward and uses standard JavaScript operators.

**Other Alternatives**

Some alternative approaches to measuring performance could include:

* Using a profiling tool like V8's `Benchmark` API (for Chrome) or the `PerformanceObserver` API.
* Creating custom microbenchmarks using a testing framework like Jest or Mocha.
* Utilizing parallel processing techniques to measure performance on multiple cores.

Keep in mind that these alternatives might require additional setup and expertise.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser/OS: Chrome 129 on Windows

View result in a separate tab

Test name	Executions per second
undefined	6503876.0 Ops/sec
typeof	17835870.0 Ops/sec
in	17852818.0 Ops/sec
operator	17735038.0 Ops/sec
bool	17962234.0 Ops/sec

Related benchmarks:

undefined vs. typeof vs. in vs. operator (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs operator vs bool

Created: 4 years ago by: Guest

Jump to the latest result

undefined

typeof

in

operator

bool

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):