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js array copy speed comparison 2
(version: 0)
Comparing performance of:
map vs array.from vs for loop vs foreach vs slice vs spread
Created:
2 years ago
by:
Registered User
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Tests:
map
const arr = [1,2,3,4,5] const newArr = arr.map(e=>e)
array.from
const arr = [1,2,3,4,5] const newArr = Array.from(arr)
for loop
const arr = [1,2,3,4,5] let newArr = []; for(let i = 0; i < arr.length; i++) { newArr[i] = arr[i]; }
foreach
const arr = [1,2,3,4,5] let newArr = [] arr.forEach(e => { newArr.push(e) })
slice
const arr = [1,2,3,4,5] const newArr = arr.slice()
spread
const arr = [1,2,3,4,5] const newArr = [ ...arr ]
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (6)
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Test case name
Result
map
array.from
for loop
foreach
slice
spread
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net. **Benchmark Overview** The provided JSON defines a benchmark that compares the performance of six different methods for creating a new array: `map`, `array.from`, `for loop`, `foreach`, `slice`, and `spread`. The test cases are identical, with the only difference being the method used to create the new array. **What is tested?** The benchmark tests the execution speed of each method on an array of five elements. The methods are compared in terms of their performance, measured in executions per second (ExecutionsPerSecond). **Options Compared** 1. `map()`: Creates a new array by applying a provided function to each element of the original array. 2. `array.from()`: Creates a new array from an existing iterable object, such as an array or string. 3. `for loop`: Iterates over the elements of the original array using a traditional for loop and assigns each value to a new array. 4. `foreach` ( likely a typo, it should be "forEach"): Similar to `map()`, but uses the `forEach()` method instead. 5. `slice()`: Creates a shallow copy of a portion of an array, starting from the specified index. 6. `spread` ( likely referring to Array.prototype spread syntax): Creates a new array by spreading the elements of an existing iterable object. **Pros and Cons** 1. **map()**: Pros: concise, readable code; Cons: can be slower due to function creation and execution. 2. **array.from()**: Pros: creates a shallow copy, which might be useful in certain scenarios; Cons: can be slower than `slice()` or `spread`. 3. **for loop**: Pros: control over iteration; Cons: verbose, error-prone code. 4. **foreach** ( corrected to "forEach"): Pros: concise, readable code; Cons: similar performance characteristics to `map()`. 5. **slice()**: Pros: fast and efficient; Cons: creates a shallow copy, which might not be suitable for all use cases. 6. **spread** ( corrected to "Array.prototype spread syntax"): Pros: concise, modern syntax; Cons: can be slower than `slice()` or other methods. **Library Usage** None of the test cases explicitly uses any external libraries. **Special JS Feature/Syntax** The benchmark uses the following features: 1. Arrow functions (`e => e`) in `map()`. 2. `Array.from()` and `spread` syntax. 3. Traditional for loop in `for loop`. These features are not specific to JavaScript version or platform, but might be more common in modern development environments. **Alternatives** Other methods for creating a new array include: 1. Using the `concat()` method: `const newArr = arr.concat();` 2. Using the `push()` method with an array: `const newArr = []; newArr.push(...arr);` 3. Using a custom reducer function in `reduce()`: `const newArr = arr.reduce((acc, e) => acc.concat(e), [])` These alternatives might have different performance characteristics and use cases compared to the methods tested in this benchmark.
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