Benchmark: typeof vs cached typeof

Script Preparation code:

var arr = [null,true,123,'',{},[]];

Tests:

uncached typeof
for(let n = 0; n < 100; n++) { arr.map((i) => { if (typeof i !== 'XXX') { return typeof i; } }); }
cached typeof
for(let n = 0; n < 100; n++) { arr.map((i) => { const typeOfI = typeof i; if (typeOfI !== 'XXX') { return typeOfI; } }); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
uncached typeof
cached typeof

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:145.0) Gecko/20100101 Firefox/145.0

Browser/OS: Firefox 145 on Windows

View result in a separate tab

Test name	Executions per second
uncached typeof	664507.6 Ops/sec
cached typeof	470383.7 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmarking test, specifically comparing the performance of two approaches: caching and not caching the `typeof` result in a loop.

**Options being compared:**

1. **Caching `typeof` result**: This approach involves storing the result of `typeof i` in a variable (`typeOfI`) before using it inside the loop. The cached result is then reused instead of recalculating it.
2. **Not caching `typeof` result**: In this approach, the result of `typeof i` is directly calculated and used inside the loop without any caching.

**Pros and Cons:**

*   **Caching `typeof` result:**
    *   Pros:
        +   Reduced calculation overhead since the result is stored once.
        +   Potential performance improvement due to reduced number of function calls.
    *   Cons:
        +   Additional memory allocation for storing the cached value.
        +   May lead to slower startup times if the cache misses are high.

*   **Not caching `typeof` result:**
    +   Pros:
        -   No additional memory overhead.
        +   Faster startup times since there's no need to store and retrieve the cached result.
    *   Cons:
        -   Higher calculation overhead due to repeated function calls.
        +   Potential performance decrease compared to caching.

**Library:**

The benchmarking test doesn't explicitly use any libraries. However, it does rely on the built-in JavaScript functions like `typeof` and array methods (`map()`).

**Special JS feature or syntax:**

This benchmark uses a common JavaScript idiom where an immediate function is used within the loop to create a closure. The syntax:

```javascript
(arr.map((i) => {
    if (typeof i !== 'XXX') {
        return typeof i;
    }
}));
```

is a concise way to perform a conditional operation on each element of the array.

**Other alternatives:**

To further optimize this benchmark, alternative approaches could be explored:

*   Using `Object.prototype.toString.call(i)` instead of `typeof` for better type detection and more robust results.
*   Employing a different data structure, like an object or a map, to store and retrieve cached values instead of using variables.

The provided options and alternative solutions can be evaluated based on specific performance requirements, memory constraints, and code readability.

Related benchmarks:

typeof vs cached typeof (version: 0)

is it worth caching a typeof result in a loop

Comparing performance of: uncached typeof vs cached typeof

Created: 3 years ago by: Guest

Jump to the latest result

uncached typeof

cached typeof

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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