class Test1 { constructor(name) { this.name = name; }}class Test2 { constructor(name) { this._name = name; } get name() { return this._name; }}class Test3 { constructor(name) { Object.defineProperties(this, { name: { enumerable : true, configurable: false, get() { return name; } } }); }}class Test4 { #name; constructor(name) { this.#name = name; } get name() { return this.#name; }}class Test5 extends Test4 {}const a20 = new Array(20).fill(undefined);function test1() { const a = new Test1('test'); return a20.map(() => a.name === 'test');}function test2() { const a = new Test2('test'); return a20.map(() => a.name === 'test');}function test3() { const a = new Test3('test'); return a20.map(() => a.name === 'test');}function test4() { const a = new Test4('test'); return a20.map(() => a.name === 'test');}function test5() { const a = new Test5('test'); return a20.map(() => a.name === 'test');}test1();test2();test3()test4();test5();--enable-precise-memory-info flag.
| Test case name | Result |
|---|---|
| test1 | |
| test2 | |
| test3 | |
| test4 | |
| test5 (by extends) |
| Test name | Executions per second |
|---|---|
| test1 | 9353361.0 Ops/sec |
| test2 | 9555166.0 Ops/sec |
| test3 | 830130.4 Ops/sec |
| test4 | 9582554.0 Ops/sec |
| test5 (by extends) | 7384350.0 Ops/sec |
Measuring JavaScript performance is a complex task, and MeasureThat.net provides a great platform for testing various scenarios.
Benchmark Definition
The provided JSON represents a benchmark that tests the execution time of different test cases in a JavaScript class with private properties and read-only properties. The benchmark defines five test cases:
test1: Creates an instance of Test1 and checks if the name property is equal to 'test'.test2: Creates an instance of Test2 and checks if the name property is equal to 'test'.test3: Uses Object.defineProperties to define a read-only property name on Test3. Then, it creates an instance of Test3 and checks if the name property is equal to 'test'.test4: Creates an instance of Test4 with a private property _name using the # symbol (also known as "private fields" in JavaScript). The test case then checks if the name property is equal to 'test'.test5: Extends Test4 and creates an instance of Test5. It then checks if the name property is equal to 'test'.Options Compared
The benchmark compares different approaches for accessing private properties:
Test1 uses a public name property.Test2 uses a getter function for its name property, which is also public.test3 uses Object.defineProperties to define a read-only property name.test4 uses the # symbol (private fields) to create a private _name property.test5 extends Test4 and inherits its private properties.Pros and Cons
Here's a brief summary of the pros and cons of each approach:
name property: Easy to access, but may not be intended for external use (e.g., due to security concerns). Pros: easy to implement, well-supported in most browsers.name property: Explicitly controls access to the private property. Pros: provides fine-grained control over accessibility; cons: can lead to boilerplate code.Object.defineProperties: Allows for more granular control over property behavior. Pros: flexible, but requires understanding of property descriptors. Cons: may be less familiar to developers.# symbol): Introduced in ECMAScript 2020, provides a concise way to declare private properties. Pros: concise and expressive; cons: relatively new feature, may not be supported in older browsers or environments.extends: Allows for code reuse by inheriting private properties from a parent class. Pros: promotes modularity, efficient code reuse; cons: may require additional setup (e.g., using classes).Other Considerations
When choosing an approach, consider the following:
Object.defineProperties or private fields.# symbol.Alternative Implementations
If you want to test other aspects of JavaScript performance, MeasureThat.net offers various benchmarks for:
Function constructors or eval)These additional benchmarks can help you identify performance bottlenecks in different areas of your JavaScript codebase.
