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Spread operator vs unshift
(version: 0)
Comparing performance of:
unshift vs spread op
Created:
4 years ago
by:
Guest
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Tests:
unshift
var l = ['apple', 7, 'omaha']; l.unshift('scarlett');
spread op
var l = ['apple', 7, 'omaha']; l = ['scarlett', ...l];
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
unshift
spread op
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
one month ago
)
User agent:
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:144.0) Gecko/20100101 Firefox/144.0
Browser/OS:
Firefox 144 on Ubuntu
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Test name
Executions per second
unshift
47689508.0 Ops/sec
spread op
43900960.0 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark and explain what's being tested. **Benchmark Definition** The benchmark definition represents two different ways to add an element to an array in JavaScript: 1. Using `Array.prototype.unshift()`: This method inserts one or more elements at the beginning of an array. 2. Using the spread operator (`...`): This operator creates a new array by copying the elements from an existing array. **Options Compared** The benchmark is comparing two options: * **Using `unshift()`**: This approach creates a copy of the original array and then inserts the new element at the beginning of the copied array. * **Using the spread operator (`...`)**: This approach uses the spread operator to create a new array with the existing elements and then adds the new element. **Pros and Cons** * **Using `unshift()`**: + Pros: Can be efficient for adding elements at the beginning of an array, as it avoids the need to copy the entire array. + Cons: Creates a temporary copy of the original array, which can be memory-intensive for large arrays. Also, if the original array is very large, this approach may not be as efficient as using the spread operator. * **Using the spread operator (`...`)**: + Pros: Efficiently creates a new array with the existing elements and adds the new element without creating a temporary copy of the original array. + Cons: May require more CPU cycles to create the new array, especially for large arrays. **Library Used** There is no library explicitly mentioned in the benchmark definition. However, it's likely that the `Array.prototype.unshift()` method is using internal implementation details from the JavaScript engine, such as the V8 engine used by Chrome. **Special JS Feature/Syntax** The benchmark uses the spread operator (`...`), which was introduced in ECMAScript 2015 (ES6). The spread operator allows you to create a new array by copying elements from an existing array or other iterable sources. **Other Considerations** When choosing between these two approaches, consider the following factors: * **Performance**: If you need to add many elements at the beginning of an array, using `unshift()` might be faster. However, for most cases, using the spread operator is a good choice. * **Memory usage**: Using `unshift()` creates a temporary copy of the original array, which can increase memory usage for large arrays. The spread operator avoids this problem. * **Readability**: Some developers may find the spread operator more readable and intuitive than using `unshift()`. However, others might prefer the explicit nature of `unshift()`. **Other Alternatives** If you need to add elements at the beginning of an array, other alternatives to `unshift()` include: * Using `Array.prototype.concat()` with a new array created from the original array. * Using `Array.prototype.slice()` followed by `Array.prototype.unshift()`. * Using a custom implementation for your specific use case. However, these alternatives may be less efficient or more memory-intensive than using `unshift()` or the spread operator.
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