Overview of the Benchmark

The provided JSON represents a JavaScript microbenchmark that tests the performance of two different approaches to check if an object has a certain property and its value is a specific type.

Benchmark Definition

The benchmark definition is:

let a = typeof (_x === null || _x === void 0 ? void 0 : _x.y) === `number`;

This line checks if the property y of an object _x exists and its value is a string that equals "number". The optional chaining operator (?.) is used to access the y property without throwing an error if it doesn't exist.

There are four test cases:

1. Optional Chaining, Not Null: Checks if the y property of _x exists and its value is a string that equals "number".
2. Explicit Null Check, Not Null: Uses an explicit null check (_x != null) to access the y property.
3. Optional Chaining, Null: Checks if the y property of an object with null value exists and its value is a string that equals "number".
4. Explicit Null Check, Null: Uses an explicit null check (_z != null) to access the y property.

Libraries and Special Features

There is no library used in this benchmark. However, there are some special features:

• The optional chaining operator (?.) was introduced in JavaScript with the release of ECMAScript 2020 (ES2020). It allows you to access nested properties without throwing an error if a null or undefined value is encountered.
• The void 0 expression is used to achieve null coalescing, which is also a new feature introduced in ES2020.

Approach Comparison

The benchmark compares the performance of two approaches:

1. Optional Chaining: Uses the optional chaining operator (?.) to access nested properties without checking for null or undefined values.
2. Explicit Null Check: Uses explicit checks (_x != null or _z != null) to ensure that the object exists before accessing its properties.

Pros and Cons of Each Approach

• Optional Chaining:
  • Pros: More concise, readable code; avoids unnecessary checks.
  • Cons: May be slower due to the additional complexity introduced by the optional chaining operator.
• Explicit Null Check:
  • Pros: Can be faster since it only checks for null or undefined values once.
  • Cons: Requires more code and can make the syntax less concise.

Other Considerations

• The benchmark uses Chrome 108 as the browser, which may affect the results due to differences in JavaScript engine optimizations between browsers.
• The DevicePlatform and OperatingSystem fields are not relevant to the performance comparison but provide additional metadata about the test environment.
• The ExecutionsPerSecond field provides a measure of the benchmark's execution frequency, which can be used to compare the performance across different browsers or versions.

Alternatives

Some possible alternatives to this benchmark could include:

• Testing other ways to check for null or undefined values, such as using the ?? operator (nullish coalescing) or explicit checks with in operator.
• Comparing the performance of optional chaining with explicit null checking in different browsers or versions.
• Using a more comprehensive test suite that covers various use cases and edge scenarios.