Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

Benchmark Definition JSON

The benchmark definition JSON provides information about the test case, including:

• Name: "Array population test"
• Description: None
• Script Preparation Code: This code is executed before running the benchmark. It sets up variables for the array size and iterations, as well as a function operate(). The purpose of this function is to populate an array with empty objects.
• Html Preparation Code: None

Test Cases

The test cases are defined in the following JSON:

[
    {
        "Benchmark Definition": "data = new Array(arraySize);\r\noperate();",
        "Test Name": "new Array"
    },
    {
        "Benchmark Definition": "data = [];\r\noperate();",
        "Test Name": "brackets"
    },
    {
        "Benchmark Definition": "data = [];\r\ndata.length=arraySize;\r\noperate();",
        "Test Name": "brackets with length"
    }
]

These test cases compare three different ways of creating an array in JavaScript:

1. new Array: Creates a new, empty array using the new keyword.
2. []: Creates a new, empty array using square brackets ([]).
3. Array constructor with length assignment: Assigns a value to the length property of an object that will be used as an array.

Options Compared

The three test cases compare different ways of creating an array, which has implications for performance and code readability.

• Pros and Cons:
  • new Array: Creates a new, empty array. Pros: more explicit creation, can be faster. Cons: requires more memory.
  • []: Creates a new, empty array using square brackets. Pros: concise syntax, often preferred by developers. Cons: may be slower due to the need for extra processing.
  • Array constructor with length assignment**: Assigns a value to the length` property of an object that will be used as an array. Pros: can be faster and more memory-efficient than the other two options. Cons: requires explicit memory management, which can add complexity.
• Other Considerations:
  • The use of new Array or [] may also affect how JavaScript engines optimize array creation. Some engines may create arrays using a different allocation strategy that takes into account the type and size of the array.

Library Used

None of the test cases explicitly uses any external libraries.

Special JS Features/Syntax

None, except for the use of const in some parts of the benchmark definition code (e.g., "var data;" is not present in the test cases).

Alternatives

Other alternatives to measure array creation performance might include:

• Using a different language or implementation that has optimized array creation.
• Implementing a custom microbenchmarking framework that allows for more fine-grained control over benchmarking scenarios.
• Running multiple benchmarks with varying input sizes and array lengths.

Keep in mind that MeasureThat.net's focus is on comparing JavaScript engine performance, so alternatives might be less relevant to the specific use case.