I'd be happy to help explain the JavaScript microbenchmark you've shared.

What is being tested?

MeasureThat.net is testing two different approaches for evaluating arithmetic expressions in JavaScript: eval() and new Function(). The benchmark compares the performance of these two methods in executing a simple arithmetic expression: 2 * 3.

Options compared

The main options being compared are:

1. eval(): A built-in JavaScript function that executes arbitrary code, including scripts and expressions.
2. new Function(): A constructor function that creates a new function object from a string of code.

Pros and cons

• eval(): Pros:
  • Easy to use: just pass the expression as a string to eval().
  • Simple syntax: no need to declare variables or define functions. Cons:
  • Performance overhead: eval() can be slower than other methods due to its dynamic nature.
  • Security risks: eval() can execute arbitrary code, making it a potential security risk if not used carefully.
• new Function(): Pros:
  • More control: allows you to define the scope and context of the function.
  • Performance: often faster than eval() since it's just executing a simple function call. Cons:
  • More verbose: requires declaring variables and defining functions before execution.
  • Less readable: can be harder to understand the intent of the code.

Other considerations

• Cached parsing: MeasureThat.net is testing if parsed expressions are cached by either eval() or new Function(). This refers to whether the JavaScript engine caches the results of parsing an expression after it's been executed once. If caching occurs, re-executing the same expression may be faster.
• Browser differences: The benchmark results show variations in performance across different browsers (in this case, Firefox 89 on a Windows desktop). This highlights the importance of testing in multiple environments to ensure your code is compatible and performs well.

Library and syntax

There are no external libraries used in these benchmarks. However, new Function() relies on JavaScript's built-in Function constructor, which is a standard feature in most modern browsers.

Special JS features or syntax

None of the benchmarking approaches rely on any special JavaScript features or syntax that would be unusual to encounter in everyday coding. The code snippets are straightforward and easy to understand.

Alternatives

If you're looking for alternative methods to evaluate expressions, consider:

• let expression: A newer feature introduced in ECMAScript 2015 (ES6), which allows defining a variable without the var, const, or let keywords.
• Template literals: Another ES6 feature that enables creating string templates with embedded expressions using backticks (`).
• with statement: Although less common, some developers use the with statement to create a scope for an expression.

Keep in mind that these alternatives might not be as widely supported or optimized as the eval() and new Function() approaches.