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getOwnPropertyNames vs loop vs cached property names
(version: 0)
Comparing performance of:
getOwnPropertyNames vs Cached property names vs for in
Created:
9 years ago
by:
Guest
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Script Preparation code:
var obj = { $names : ['a','b','c'], a:1, b:2, c:3 }
Tests:
getOwnPropertyNames
var ks = Object.getOwnPropertyNames(obj); var n = 0; for (var i = 0; i < ks.length; i++) { var k = ks[i]; if (k.charAt(0) == '$') continue; n++; }
Cached property names
var ks = obj['$names']; var n = 0; for (var i = 0; i < ks.length; i++) { var k = obj[ks[i]]; n++; }
for in
var n = 0; for (var k in obj) { if (k.charAt(0) == '$') continue; n++; }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (3)
Previous results
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Test case name
Result
getOwnPropertyNames
Cached property names
for in
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Measuring the performance of different approaches to iterate over an object's properties is crucial in understanding the underlying mechanics of JavaScript's `for...in` loop, `Object.getOwnPropertyNames()`, and accessing properties via arrays. **Options being compared:** 1. **getOwnPropertyNames()**: This method returns an array containing all the property names of an object. 2. **Loop with manual property iteration**: This involves looping through the `Object.getOwnPropertyNames()` result and checking if each property name starts with a `$` (indicating it's not a special property). If it does, it skips that iteration. 3. **Cached property names**: This approach uses the `$names` array directly to iterate over its elements, accessing the corresponding properties via bracket notation (`obj[ks[i]]`). **Pros and Cons of each approach:** 1. **getOwnPropertyNames()**: * Pros: + Efficient, as it only requires one pass through the object's properties. + Reduces overhead associated with manual property iteration. * Cons: + May be slower due to the extra function call and array access. 2. **Loop with manual property iteration**: * Pros: + Provides explicit control over the iteration process, allowing for potential optimizations or handling of special properties. * Cons: + Requires more CPU cycles due to the additional loop overhead. 3. **Cached property names**: * Pros: + Similar performance characteristics to `getOwnPropertyNames()`, as it leverages the optimized array access. * Cons: + Only works if `$names` is an array, which might not be the case for all objects. **Library usage:** None of the benchmark cases explicitly use a library. However, some JavaScript engines (like V8 in Chrome) provide built-in optimizations and features that can influence performance. **Special JS feature or syntax:** There are no explicit special features or syntaxes mentioned in the benchmark definition. The `$names` array is used as an array literal, which is a standard JavaScript syntax. **Other considerations:** 1. **Browser variability**: Different browsers might exhibit varying performance due to their respective engines and optimization strategies. 2. **Object structure**: The specific object being tested can impact performance, especially if it contains many properties or has complex internal structures. **Alternative approaches:** Some possible alternative approaches for iterating over an object's properties include: 1. Using a `for...in` loop with the `hasOwnProperty()` method to filter out special properties. 2. Utilizing the `Object.keys()` method, which returns an array of property names. 3. Leveraging modern JavaScript features like `for...of` loops or `Map`/`Set` objects for iteration. However, these alternatives are not explicitly tested in this benchmark case.
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