Benchmark: Caching length property (internal and external) vs getting it each time in the loop, v2

Script Preparation code:

var arr = [];
var count = 10000;
for(var i = 0; i<count; i++)
{
  arr.push(i);
}

Tests:

Cache length (external)
var arrLen = arr.length; var sum = 0; for (var i = 0; i < arrLen; i++){ sum = arr[i]; }
No cache
var sum = 0; for (var i = 0; i < arr.length; i++){ sum = arr[i]; }
Cache length (internal)
var sum = 0; for (var i = 0, arrLen = arr.length; i < arrLen; i++){ sum = arr[i]; }
Reverse loop, internal cache (var)
var sum = 0; for (var i = arr.length; i--; ){ sum = arr[i]; }
Reverse loop, internal cache (let)
let sum = 0; for( let i = arr.length; i--; ){ sum = arr[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Cache length (external)
No cache
Cache length (internal)
Reverse loop, internal cache (var)
Reverse loop, internal cache (let)

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the benchmark.

**Benchmark Overview**

The benchmark measures the performance difference between using an external variable to store the length of an array versus accessing it directly within a loop in JavaScript. There are four test cases:

1. "Cache length (external)": This test case uses an external variable `arrLen` to store the length of the array and then accesses it within the loop.
2. "No cache": This test case does not use any caching mechanism and accesses the `length` property directly on the array within the loop.
3. "Cache length (internal)": This test case uses a single variable declaration inside the loop to store the length of the array, effectively "caching" it for each iteration.
4. "Reverse loop, internal cache (var)" and "Reverse loop, internal cache (let)": These two test cases use similar caching mechanisms as above, but with the `var` keyword instead of a single variable declaration.

**Options Compared**

The benchmark compares four different approaches:

1. **External Variable**: Using an external variable to store the length of the array.
2. **No Cache**: Accessing the `length` property directly on the array within the loop without any caching mechanism.
3. **Internal Cache (Var)**: Using a single `var` declaration inside the loop to store the length of the array, effectively "caching" it for each iteration.
4. **Reverse Loop with Internal Cache**: Similar to the previous point, but using a single variable declaration to store the length of the array, even in reverse loops.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **External Variable**:
	+ Pros: Easy to understand, simple implementation.
	+ Cons: Requires an extra line of code, may increase memory usage.
* **No Cache**:
	+ Pros: Simple, no additional memory usage required.
	+ Cons: May result in slower performance due to repeated array lookups.
* **Internal Cache (Var)**:
	+ Pros: Reduces the number of array lookups, can improve performance.
	+ Cons: Can be less intuitive for developers who are not familiar with this pattern.
* **Reverse Loop with Internal Cache**:
	+ Pros: Similar benefits as above, but applied to reverse loops.
	+ Cons: May require additional understanding of variable scope and hoisting.

**Library Usage**

None of the test cases use any external libraries or frameworks. The benchmark only focuses on JavaScript core functionality.

**Special JS Features/Syntax**

The benchmark does not mention any special JavaScript features or syntax, as it only involves basic array operations and caching mechanisms.

**Alternative Approaches**

Other alternatives to consider for similar benchmarks might include:

* Using `const` instead of `var` for internal caching
* Implementing a more sophisticated caching mechanism using objects or arrays
* Comparing the performance of different JavaScript engines (e.g., V8, SpiderMonkey)
* Adding additional complexity to the benchmark by introducing more variables, loops, or data structures.

Related benchmarks:

Caching length property (internal and external) vs getting it each time in the loop, v2 (version: 0)

save length of the array in the variable vs get it the loop

Comparing performance of: Cache length (external) vs No cache vs Cache length (internal) vs Reverse loop, internal cache (var) vs Reverse loop, internal cache (let)

Created: 3 years ago by: Guest

Jump to the latest result

Cache length (external)

No cache

Cache length (internal)

Reverse loop, internal cache (var)

Reverse loop, internal cache (let)

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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