The benchmark "Nested with statements" evaluates the performance of JavaScript functions that use the with statement in varying nested levels. The with statement extends the scope chain for the duration of the block, allowing for the properties of an object to be accessed directly without needing to reference the object each time. In this benchmark, the focus is on testing how the use of multiple with statements impacts the execution speed.

Benchmarked Options

1. Normal: This test case runs the basic function go0() without any with statements.
2. 1 with statement: go1() introduces one with statement, encapsulating the property access within the object myObj.
3. 2 with statements: go2() adds a second with statement, increasing the complexity of the scope chain.
4. 3 with statements: go3() increases this to three nested with statements.
5. 4 with statements: go4() extends it to four nested with statements.

Results Overview

The results show a substantial decline in performance as the number of nested with statements increases. Here are the raw performance metrics in executions per second for each scenario:

• Normal: 88,875,592.0 executions/second
• 1 with statement: 3,980,551.25 executions/second
• 2 with statements: 2,356,184.0 executions/second
• 3 with statements: 1,562,563.75 executions/second
• 4 with statements: 1,176,462.5 executions/second

Pros and Cons

Pros of using with:

• It can simplify code for accessing properties of an object, reducing repetitive code when accessing multiple properties.

Cons:

• Performance Implications: As seen in the benchmark results, using multiple with statements can significantly degrade performance due to increased complexity in scope resolution.
• Readability and Maintainability: Code that uses with can be harder to read and understand, especially for those unfamiliar with it, and can lead to bugs if object properties conflict with variables in the same scope.
• Variable Scope Issues: The with statement creates potential pitfalls by adding properties to the local scope which might lead to confusing bugs or unexpected behaviors.

Library/Feature Considerations

In this benchmark, no external libraries are used; the tests are purely based on native JavaScript behavior and its intrinsic with statement.

Alternative Approaches

• Use of Closures: Instead of with, closures can be used to create a scoped context where the properties can be accessed directly. This often retains performance benefits and improves readability.
• Destructuring Assignment: Using destructuring can simplify property access without the performance hit of with. For example, const {property} = myObj allows direct access to property.
• Explicit Scope: Simply referencing an object directly using myObj.property can often be clearer and avoids ambiguity, making debugging easier.

Conclusion

This benchmark illustrates the clear performance degradation associated with using multiple with statements, reinforcing the idea that while syntactic sugar might make for concise code, it can lead to hidden costs in performance and maintainability. Software engineers should consider alternative structural approaches to maintain both performance and readability in their JavaScript code.