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for-in vs for-of entries
(version: 0)
Comparing performance of:
for-in vs for-of Object.entries
Created:
4 years ago
by:
Guest
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Script Preparation code:
var obj = { 'a': 1, 'b': 1, 'c': 1, 'd': 1, 'e': 1, 'f': 1, 'g': 1 };
Tests:
for-in
for (var i=10000; i > 0; i--) { for (var key in obj) { console.log(key); console.log(obj[key]); } }
for-of Object.entries
for (var i=10000; i > 0; i--) { for (var [ key, value ] of Object.entries(obj)) { console.log(key); console.log(value); } }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
for-in
for-of Object.entries
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
**Overview of the Benchmark** The provided JSON represents a JavaScript benchmark test that compares the performance of two `for` loops: one using the traditional `in` operator (`for-in`) and another using the `of` syntax with `Object.entries`. The benchmark is designed to measure which approach is faster in terms of executions per second. **Options Compared** The benchmark tests two options: 1. **Traditional `for-in` loop**: This loop uses the `in` operator to iterate over the properties of an object, which returns a property name (key) and the corresponding value. 2. **`of` syntax with `Object.entries`**: This loop uses the `of` syntax to create an iterator that iterates over the key-value pairs of an object, obtained from `Object.entries()`. **Pros and Cons** * **Traditional `for-in` loop:** + Pros: - Widely supported across older browsers. - Simple and easy to understand for developers. + Cons: - Can be slower due to the need to manually increment a counter or use a different data structure to maintain iteration state. * **`of` syntax with `Object.entries`:** + Pros: - More modern and efficient, as it leverages built-in iterator functionality. - Easier to read and write for developers familiar with array methods. + Cons: - May not be supported in older browsers or by JavaScript engines that don't have a strong understanding of the `of` syntax. **Library Used** The benchmark uses the `Object.entries()` method, which is a modern JavaScript feature introduced in ECMAScript 2015 (ES6). This method returns an array of key-value pairs for an object, allowing developers to create iterators and iterate over the properties of an object in a more efficient and expressive way. **Special JS Feature/Syntax** The benchmark uses the `of` syntax with `Object.entries()`, which is a modern JavaScript feature. The `of` syntax was introduced in ECMAScript 2016 (ES7) and allows developers to create iterators from arrays, objects, or generators. In this case, it's used to create an iterator over the key-value pairs of an object. **Other Alternatives** If you're interested in exploring alternative approaches to the `for-in` loop, here are some options: 1. **`for...in` loop with a counter**: You can use a traditional `for` loop with a manually incremented counter instead of using the `in` operator. 2. **`forEach()` method**: You can use the `forEach()` method to iterate over an array or object, but this approach might not be as efficient as using `Object.entries()` and the `of` syntax. 3. **Generators**: You can use generators to create iterators that yield values on demand, which can be more memory-efficient than creating arrays or objects. Keep in mind that these alternatives might have different performance characteristics and trade-offs compared to the traditional `for-in` loop or the `of` syntax with `Object.entries()`.
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