The benchmark is designed to compare two methods of creating a new array by adding an element to an existing array in JavaScript: the traditional Array.prototype.concat() method and the newer ES6 spread operator (...[ ]).

Options Compared

1. Array.prototype.concat():

   • This is the traditional method for combining arrays and adding elements. Here is how it works in the benchmark:
     • Test Case: var other = big.concat(2);
     • This creates a new array that consists of all elements of the big array followed by the element 2.

2. Spread Operator:

   • The spread operator is a syntactical feature introduced in ES6 (ECMAScript 2015) that allows an iterable (like an array) to be expanded into individual elements. In this benchmark:
     • Test Case: var other = [ ...big, 2 ];
     • This creates a new array by placing the elements of big followed by 2 in a more concise manner, effectively "spreading" the elements.

Pros and Cons

Array.prototype.concat()

• Pros:

  • Compatible with earlier versions of JavaScript; useful for maintaining support with legacy systems.
  • Clear and straightforward for those familiar with traditional array manipulation methods.

• Cons:

  • Typically slower than the spread operator in modern JavaScript engines, as seen in this benchmark result.
  • More verbose than using the spread operator, especially with long arrays.

Spread Operator

• Pros:

  • More concise and easier to read, reducing boilerplate code.
  • Generally has better performance according to benchmarks, as evidenced by the results in this specific test.
  • Can be more flexible for various use cases, such as merging multiple arrays or copying an array with slight modifications.

• Cons:

  • Requires ES6 support, which might be an issue in very old browsers or environments that do not support this feature.
  • May be less familiar to developers who have only worked with older versions of JavaScript.

Benchmark Results

The results indicate that Array.prototype.concat executed 4059.22 times per second, while the spread operator executed 2778.96 times per second. This suggests that in this particular test case, concat() outperformed the spread operator, which may be surprising given the general expectations about performance with modern JavaScript practices. This discrepancy may be due to various factors like JS engine optimizations or the specific nature of the test setup.

Other Considerations

• The choice between these two methods may depend not only on performance but also on code readability and maintainability.
• Developers should consider current browser compatibility when opting for the spread operator, though most modern browsers fully support ES6 features as of now.
• If performance is critical, it's recommended to profile both methods in the specific context they will be used, rather than relying solely on general benchmarks.

Alternatives

There are other alternatives to concatenate or merge arrays in JavaScript, such as:

• Array.prototype.push(): This method can be used in combination with the spread operator to push elements into an existing array.
• Array.prototype.unshift(): Similar to push(), but adds elements to the start of the array.
• Array.concat() with a variable number of arrays: You can use this method to merge multiple arrays together.
• Performing array manipulations with helper libraries like Lodash, which provides many utilities for handling arrays and objects in a more functional style.

In conclusion, the benchmark effectively highlights the comparison of two significant features in JavaScript for array manipulation, weighing both performance and coding style in the context of modern coding practices.