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Comparing performance of:
for let vs for var vs for let cached vs for let cached (const) vs for var cached vs forEach
Created:
4 years ago
by:
Registered User
Jump to the latest result
Script Preparation code:
var array = []; for (var i=0, t=10000; i<t; i++) { array.push(Math.round(Math.random() * t)) } var t=0;
Tests:
for let
for (let i = 0; i < array.length; i++) { t += array[i]; }
for var
for (var i = 0; i < array.length; i++) { t += array[i]; }
for let cached
let len=array.length; for (let i = 0; i < len; i++) { t += array[i]; }
for let cached (const)
const len=array.length; for (let i = 0; i < len; i++) { t += array[i]; }
for var cached
var len=array.length; for (var i = 0; i < len; i++) { t += array[i]; }
forEach
array.forEach(function(v, i) { t += v; });
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (6)
Previous results
Fork
Test case name
Result
for let
for var
for let cached
for let cached (const)
for var cached
forEach
Fastest:
N/A
Slowest:
N/A
Latest run results:
No previous run results
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark data. **Benchmark Purpose** The benchmark measures the performance of different JavaScript iteration methods in executing a simple calculation on an array of numbers. The goal is to determine which method is the fastest. **Iteration Methods Compared** The benchmark compares six different iteration methods: 1. **for let**: A traditional `for` loop with the `let` keyword for variable declaration. 2. **for var**: A traditional `for` loop with the `var` keyword for variable declaration. 3. **for let cached (const)**: Similar to `for let`, but uses a constant variable declaration (`const`) instead of re-declaration on each iteration. 4. **forEach**: The `Array.prototype.forEach()` method, which calls a callback function once for each element in the array. **Pros and Cons of Each Approach** 1. **for let**: * Pros: More modern syntax, no need to declare variable before use, better scoping. * Cons: May incur overhead due to re-declaration on each iteration. 2. **for var**: * Pros: Legacy syntax, widely supported by older browsers. * Cons: Outdated syntax, potential naming conflicts, and scope issues. 3. **for let cached (const)**: * Pros: Combines the benefits of modern syntax with a constant variable declaration for performance optimization. * Cons: May require careful consideration of when to use `const` vs `let`. 4. **forEach**: * Pros: Native method, optimized for iteration, and concise syntax. * Cons: May incur overhead due to callback function execution, and less control over iteration logic. **Library Usage** There is no explicit library usage mentioned in the benchmark definition or test cases. **Special JavaScript Features or Syntax** No special features or syntax are used beyond what's already described above. However, it's worth noting that `forEach` method uses a callback function, which may incur additional overhead compared to traditional loops. **Alternative Benchmarks** Other alternatives for benchmarking iteration performance could include: * Using a more complex array operation (e.g., sorting, filtering) * Incorporating concurrency or parallelization * Comparing different JavaScript engines (e.g., V8, SpiderMonkey) or browsers * Adding noise or variability to the benchmark inputs to simulate real-world usage
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