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spread vs concat vs unshift223
(version: 0)
spread vs concat vs unshift
Comparing performance of:
arrayUnshift123 vs arrayConcat123 vs arraySpread123 vs reduce123
Created:
3 years ago
by:
Guest
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Script Preparation code:
var array = new Array(10).fill(0);
Tests:
arrayUnshift123
const r = array.slice().unshift(0);
arrayConcat123
const r = array.concat([0])
arraySpread123
const r = array = [0, ...array]
reduce123
const r = array.reduce((acc, cur) => { acc.push(cur); return acc; }, [0])
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (4)
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Test case name
Result
arrayUnshift123
arrayConcat123
arraySpread123
reduce123
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons. **Benchmark Purpose:** The provided benchmark compares the performance of three different methods to add an element to an array: 1. `unshift()` 2. `concat()` with a single-element array 3. Using the spread operator (`...`) **Comparison Options:** * `unshift()`: Adds an element to the end of the array and shifts all subsequent elements to the right. * `concat()`: Creates a new array by copying the original array's elements followed by the given element (in this case, a single-element array). * Using the spread operator (`...`): Creates a new array with the given element(s) prepended to the existing array. **Pros and Cons of Each Approach:** 1. **`unshift()`**: * Pros: * Efficient for small arrays since it only requires updating the elements' indices. * Simple implementation in most browsers. * Cons: * Can be slower for large arrays due to the need to shift all subsequent elements, which results in a higher number of temporary copies. * Not as widely supported in older JavaScript versions or non-browser environments (e.g., Node.js). 2. **`concat()`**: * Pros: * Generally faster than `unshift()`, especially for large arrays. * More widely supported across different browsers and platforms, including older ones. * Cons: * Creates a new array object, which can be memory-intensive for large datasets. * Requires two operations: one for creating the new array and another for assigning it to `r`. 3. **Using the Spread Operator (`...`)**: * Pros: * Fastest approach, as it only requires a single operation to create the new array. * Memory-efficient since it doesn't require copying all elements or creating multiple temporary arrays. * Cons: * Not supported in older JavaScript versions (before ECMAScript 2018). * May not work correctly in some browser versions due to variations in their implementations. **Library:** None. This benchmark uses native JavaScript features and built-in array methods without relying on external libraries or frameworks. **Special JS Feature/Syntax:** The spread operator (`...`), introduced in ECMAScript 2018 (ES8) under the name "Rest property" and further developed as a feature called "Spread operator" or simply "spread syntax". This is used to expand an array expression into separate arguments when passing an array to a function. **Other Alternatives:** For creating arrays, other methods can be used instead of `unshift()`, `concat()`, or the spread operator. These include: * Using `Array.prototype.push()` followed by `Array.prototype.shift()`: This method updates the original array but is less efficient than using the spread operator for large datasets. * Creating an array with the `new` keyword and pushing elements to it: This method can be memory-intensive if you need to push many elements. Here's a sample implementation of these alternatives: ```javascript // Using push() followed by shift() const result1 = new Array(10).fill(0); result1.push(0); let r = []; for (let i = 9; i >= 0; i--) { r.push(result1[i]); } // Creating an array with the 'new' keyword const result2 = new Array(10).fill(0); r = [0, ...result2]; ``` However, the spread operator remains a preferred choice due to its simplicity and efficiency.
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