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

The benchmark being tested is the comparison between two approaches: using a traditional switch statement and using an object lookup (also known as a hash table or associative array). The goal is to determine which approach is faster for this specific use case.

Switch Statement

The switch statement is used in the first test case. It takes an input value of 10 and checks if it matches any of the cases defined in the switch block. If a match is found, the corresponding code inside the case block is executed.

Here's what's happening under the hood:

1. The JavaScript engine parses the switch statement and generates a jump table (a data structure that maps values to indices) based on the input value.
2. When the input value is 10, the engine jumps directly to the corresponding case block.
3. Inside the case block, the code checks if the input value matches any of the cases using a simple equality check.

Object Lookup (Map)

The second test case uses an object lookup instead of a traditional switch statement. The same input value of 10 is used to access a hash table (LUT) that maps values to boolean results.

Here's what's happening under the hood:

1. The JavaScript engine creates a new hash table (LUT) that contains key-value pairs for the possible input values (0-10).
2. When the input value of 10 is used, the engine looks up the corresponding boolean result in the LUT using the input value as the key.
3. If a match is found, the resulting boolean value is returned.

Comparison

Now, let's talk about the pros and cons of each approach:

Switch Statement:

Pros:

• Simple to understand and implement
• Can be more readable for small codebases
• Uses less memory compared to an object lookup

Cons:

• Performance can degrade for large numbers of cases
• May not perform well with floating-point or complex comparisons
• Generates a jump table, which can increase memory usage

Object Lookup (Map):

Pros:

• Fast and efficient for lookups
• Can handle large numbers of cases without performance degradation
• Uses hash tables, which are optimized for fast lookups

Cons:

• More memory-intensive compared to switch statements
• Requires more complex code to implement
• May be less readable due to the need to define a hash table upfront.

Other Considerations

When using object lookup, it's essential to consider the following factors:

• Cache performance: If the LUT is large and contains many identical values, cache performance may improve.
• Memory usage: The size of the LUT will impact memory usage. Large hash tables can lead to increased memory allocation.

Special JS Features

There are no special JavaScript features or syntax mentioned in this benchmark. However, it's worth noting that some modern browsers support features like const enum for switch-like statements and optimized hash table lookups.

Alternatives

If you're looking for alternative approaches to this benchmark, consider the following:

• Array-based approach: Instead of using a hash table, use an array with index values corresponding to the input values. This can be faster than object lookup but may require more memory.
• Binary search: Use binary search algorithms to find the matching value in the LUT. This can be faster for large hash tables but may require more complex code.

In conclusion, this benchmark compares two approaches: traditional switch statements and object lookups (hash tables). The choice between these approaches depends on performance requirements, memory constraints, and readability considerations.