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.concat vs. spread
(version: 0)
Compares performance of array .concat() method and array spreads.
Comparing performance of:
.concat vs spread
Created:
4 years ago
by:
Guest
Jump to the latest result
Script Preparation code:
var arr1 = [1,2,3]; var arr2 = [4,5,6];
Tests:
.concat
var result = arr1.concat(arr2);
spread
var result = [...arr1, ...arr2];
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
.concat
spread
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the world of JavaScript microbenchmarks! **What is being tested?** The provided JSON represents a benchmark that compares the performance of two ways to concatenate arrays in JavaScript: using the `.concat()` method and using array spreads. **Options compared:** * `.concat()`: The original way of concatenating arrays in JavaScript, which creates a new array by copying elements from the source arrays. * Spread (`...`): A newer syntax introduced in ECMAScript 2015 (ES6) that allows for more concise and expressive array creation. **Pros and Cons:** * `.concat()`: Pros: + Widely supported across different browsers and platforms. + Can be used with older JavaScript versions that don't support spread syntax. + Allows for more control over the resulting array structure (e.g., modifying individual elements). Cons: + Creates a new array, which can lead to performance issues if dealing with large datasets. + Less readable code compared to spread syntax. * Spread (`...`): Pros: + More concise and expressive code. + Creates a new array in a more efficient way than `.concat()`. + Improved readability. Cons: + May not work in older JavaScript versions or browsers that don't support it. + Less control over the resulting array structure. **Library usage:** There is no specific library mentioned in the benchmark definition. However, note that some libraries like Lodash might provide additional methods for working with arrays, which could affect performance. **Special JS features or syntax:** The benchmark uses ES6 spread syntax (`...`) introduced in ECMAScript 2015. This syntax allows for more concise array creation and has improved readability. **Benchmark preparation code:** The script prepares two arrays, `arr1` and `arr2`, with elements `[1,2,3]` and `[4,5,6]`, respectively. The benchmark definition tests the performance of concatenating these arrays using both `.concat()` and spread syntax. **Other alternatives:** Besides `.concat()` and spread syntax, there are other ways to concatenate arrays in JavaScript: * Using the `Array.prototype.push()` method with an array as an argument (e.g., `arr1.push(arr2)`). * Using a loop to append elements from one array to another. * Using the `Array.prototype.concat()` method's variant that returns a new array without modifying the original (e.g., `[...arr1, ...arr2]`). However, these alternatives are not typically used in production code due to their performance implications or lack of conciseness. **Benchmark execution results:** The latest benchmark result shows that Mobile Safari 15 on an iOS device executes `.concat()` approximately 37.8% faster than spread syntax (4945522.5 executions per second vs. 4567629.5 executions per second, respectively). However, this result may vary depending on the specific test environment and hardware. Keep in mind that JavaScript engines can optimize performance-critical code in various ways, so these results should be taken as a general guideline rather than absolute proof of performance differences.
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