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for-in vs object.keys with for
(version: 0)
Comparing performance of:
for-in vs Object.keys
Created:
5 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, 'h': 1, 'i': 1, 'j': 1, 'k': 1, 'l': 1, 'm': 1, 'n': 1, 'o': 1, 'p': 1, 'q': 1, 'r': 1, 's': 1, 't': 1, 'u': 1, 'v': 1, 'w': 1, 'x': 1, 'y': 1, 'z': 1, 'aa': 1, 'ba': 1, 'ca': 1, 'da': 1, 'ea': 1, 'fa': 1, 'ga': 1, 'ha': 1, 'ia': 1, 'ja': 1, 'ka': 1, 'la': 1, 'ma': 1, 'na': 1, 'oa': 1, 'pa': 1, 'qa': 1, 'ra': 1, 'sa': 1, 'ta': 1, 'ua': 1, 'va': 1, 'wa': 1, 'xa': 1, 'ya': 1, 'za': 1, 'ab': 1, 'bb': 1, 'cb': 1, 'db': 1, 'eb': 1, 'fb': 1, 'gb': 1, 'hb': 1, 'ib': 1, 'jb': 1, 'kb': 1, 'lb': 1, 'mb': 1, 'nb': 1, 'ob': 1, 'pb': 1, 'qb': 1, 'rb': 1, 'sb': 1, 'tb': 1, 'ub': 1, 'vb': 1, 'wb': 1, 'xb': 1, 'yb': 1, 'zb': 1 };
Tests:
for-in
for (var i=10000; i > 0; i--) { for (var key in obj) { if (obj.hasOwnProperty(key)) { console.log(key); } } }
Object.keys
for (var i=10000; i > 0; i--) { var keys = Object.keys(obj); for (var j = 0; j < keys.length; j ++) { console.log(keys[j]); } }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
for-in
Object.keys
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! **Benchmark Definition** The provided benchmark definition represents two test cases: 1. `for-in vs object.keys with for` 2. Two individual test cases: * `for-in` * `Object.keys` These test cases aim to compare the performance of three approaches: `for-in`, `object.keys`, and a combination of both (`for-in` with `object.keys`). **What is tested** The benchmark tests the execution speed of each approach on a large object with 32 properties, ranging from 'a' to 'za'. The test case measures how many iterations of logging the property names are executed per second. **Options compared** There are three options being compared: 1. **for-in**: This approach uses the `for-in` loop to iterate over the object's properties. It has some limitations, as it: * Iterates over both enumerable and non-enumerable properties. * Can be slow due to its inherent overhead. 2. **object.keys**: This approach uses the `Object.keys()` method to get an array of property names. It is generally faster than `for-in` but may still have some overhead due to string manipulation. 3. **Combination of for-in and object.keys**: In this variant, the test case first retrieves the property names using `object.keys()`, and then uses a second `for-in` loop to iterate over them. **Pros and Cons** Here's a brief summary of each approach: * **for-in**: + Pros: Easy to implement and understand. + Cons: Can be slow due to its inherent overhead, and may not work correctly for non-enumerable properties. * **object.keys**: + Pros: Generally faster than `for-in`, as it avoids the overhead of iterating over all properties. + Cons: May still have some overhead due to string manipulation, and requires a JavaScript engine that supports `Object.keys()`. * **Combination**: + Pros: Can potentially avoid the overhead of the first `for-in` loop by retrieving property names beforehand. + Cons: Introduces additional complexity and may not always be faster than using `object.keys()` directly. **Library usage** The benchmark uses no libraries, as it only involves built-in JavaScript functionality. **Special JS feature/syntax** There are no special JavaScript features or syntax used in this benchmark. The tests use standard JavaScript loops and methods. **Alternatives** If you'd like to explore alternative approaches or variations on these benchmarks, consider the following: * **Iterating over object entries**: You can use `Object.entries()` to get an array of key-value pairs, which might offer better performance than using `object.keys()` or `for-in`. * **Using a custom iterator**: You could create a custom iterator that uses a more efficient algorithm for iterating over the properties, such as one that uses bit manipulation or bitwise operations. * **Comparing with other languages**: You can modify the benchmark to test performance in other languages, such as Python or C++, to compare their iteration efficiency. I hope this explanation helps you understand the JavaScript microbenchmark!
Related benchmarks:
for-in vs object.keys with for loop large obj fixed
for..in vs for loop using Object.keys
for-in vs for..of object.keys
Object.keys vs for-in
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