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defineproperty vs direct assignment, accessing (4)
(version: 2)
Comparing performance of:
a vs b
Created:
4 years ago
by:
Registered User
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Tests:
a
var target = {}; for (var i=0; i<4; i++) { Object.defineProperty(target, i, { value:i }); } for (var j=0; j<500; j++) { console.log(target[0], target[1], target[2], target[3]); }
b
var target = {}; for (var i=0; i<4; i++) { target[1] = i; } for (var j=0; j<500; j++) { console.log(target[0], target[1], target[2], target[3]); }
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Suite status:
<idle, ready to run>
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Result
a
b
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Slowest:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
**Benchmark Overview** MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The benchmark in question compares the performance of two approaches: using `Object.defineProperty` to assign values to an object's properties, versus direct assignment using bracket notation (`target[i] = i;`). **Options Compared** The benchmark tests two options: 1. **Using `Object.defineProperty`**: This approach uses the `Object.defineProperty` method to define a property on an object. The `value` option is specified in the descriptor, which allows for fine-grained control over the property's behavior. 2. **Direct Assignment using Bracket Notation**: This approach uses direct assignment using bracket notation (`target[i] = i;`) to assign values to an object's properties. **Pros and Cons of Each Approach** ### Using `Object.defineProperty` Pros: * **Flexibility**: `Object.defineProperty` provides a flexible way to define properties on objects, allowing for custom descriptors that can be used to optimize performance. * **Memory Efficiency**: By using `Object.defineProperty`, the benchmark can avoid allocating new memory for each property assignment. Cons: * **Overhead**: Creating an object descriptor and defining a property can introduce some overhead compared to direct assignment. * **Browser Support**: Although widely supported, some older browsers may not have implemented `Object.defineProperty` correctly. ### Direct Assignment using Bracket Notation Pros: * **Simpllicity**: Direct assignment using bracket notation is simple and easy to understand. * **Wide Browser Support**: This approach is widely supported across most modern browsers. Cons: * **Performance Overhead**: Creating a new property assignment can introduce performance overhead compared to `Object.defineProperty`. * **Memory Allocation**: Each property assignment requires allocating new memory for the object, which can be inefficient. **Other Considerations** * **Cacheability**: The benchmark's results may depend on cache locality and evictions. Since both approaches use a single array `target` as the base object, this could potentially introduce interesting caching effects. * **Garbage Collection**: The JavaScript engine's garbage collection strategy might also influence the performance differences between these two approaches. **Library Usage** There is no specific library used in this benchmark other than built-in JavaScript features. However, some implementations of `Object.defineProperty` or bracket notation might rely on external libraries for additional functionality. **Special JS Feature or Syntax** The benchmark does not use any special JavaScript feature or syntax beyond the standard language features and built-ins. **Alternative Approaches** Some alternative approaches to compare in this benchmark could include: * Using `Array.prototype.forEach` instead of direct assignment. * Using `Object.create(null)` to initialize the object, potentially offering a different performance profile compared to using an existing object (`target = {};`). * Comparing with other property access patterns, such as `target[i] = i;` vs. `target[i] = target[0];` However, these alternatives might not directly address the core question of `Object.defineProperty` vs. direct assignment, and would likely require additional benchmark setup to provide meaningful insights.
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