Benchmark Overview

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks, comparing different approaches to achieve the same goal. In this case, we have two test cases: "Object assign" and "Object spread". The benchmark measures which approach is faster, using a specific dataset provided in the Benchmark Definition JSON.

Benchmark Definition JSON

The Benchmark Definition JSON contains information about the script preparation code, which defines an object first with various properties, including nested objects and functions. This object will be used to test two different approaches: object assignment (Object.assign) and object spread (...).

The Script Preparation Code is:

var first = {
  foo: "string",
  bar: 42,
  baz: 100.56,
  quux: "another string",
  foobar: {
    one: "foo bar",
    two: "bar foo"
  },
  bazbaz: function (a, b) {
    return a * a % b + 100 / b;
  }
};

var second = {
  one: "x",
  two: "y",
  three: "z",
  x: "one",
  y: "two",
  z: "three",
  foo: "string 2",
  bar: 43
};

Options Compared

Two options are compared:

1. Object assignment (Object.assign): This approach uses the Object.assign() method to merge two objects into a new object.

const third_assign = Object.assign({}, first, second);
return third_assign;

2. Object spread (...): This approach uses the spread operator (...) to create a new object with properties from both first and second.

const third_spread = {
  ...first,
  ...second,
};
return third_spread;

Pros and Cons

Object assignment (Object.assign)

Pros:

• More explicit and readable code
• Works well for merging objects with simple property names

Cons:

• Can be slower due to the overhead of function calls
• May not work as expected if properties have different types (e.g., numbers vs strings)

Object spread (...)

Pros:

• Faster and more concise code
• Works well for merging objects with simple property names
• Supports nested objects and arrays

Cons:

• Less explicit and readable code (may require additional configuration)
• May not work as expected if properties have different types (e.g., numbers vs strings)

Library and Special JS Feature

There is no specific library used in this benchmark, but it does use the spread operator (...), which is a modern JavaScript feature introduced in ECMAScript 2018.

Other Considerations

• Performance: The benchmark measures performance by executing each test case multiple times and measuring the execution time.
• Platform dependence: The benchmark runs on different devices (Desktop) and browsers (Chrome 84).
• Test duration: The benchmark executes each test case for a certain number of executions per second.

Alternatives

Other alternatives to these approaches could include:

1. Using a library like Lodash or Ramda, which provides a more functional programming style for merging objects.
2. Using a different data structure, such as an array or a JSON object with custom merge functions.
3. Optimizing the benchmark code using techniques like memoization or caching.

However, these alternatives may not be relevant to this specific benchmark, which focuses on comparing two basic approaches to merging objects: object assignment and object spread.