Let's dive into the world of JavaScript microbenchmarks!

Benchmark Overview

The provided JSON represents a benchmark test that compares two approaches: Map.get() and Map.has() + Map.get(). The test is designed to measure the performance difference between these two methods in retrieving values from a large Map object.

Script Preparation Code

The script preparation code creates a new Map object, map, and populates it with 20,000 key-value pairs using the set() method. The keys are generated dynamically using string concatenation (i + '_' + '_g').

var i = 0, count = 20000, a;
var map = new Map();
for (i = 0; i < count; i++) {
  map.set(i + '_' + '_g', i);
}

Html Preparation Code

The HTML preparation code is null, indicating that no specific HTML structure or content is required for this benchmark.

Test Cases

There are two test cases:

1. Map get: This test case uses the map.get() method to retrieve values from the Map object.

for (i = 0; i < count; i++) {
  a = map.get(i + '_' + '_g');
}

2. Map has get: This test case uses the map.has() method to check if a key exists in the Map, and then retrieves the value using map.get().

for (i = 0; i < count; i++) {
  let key = i + '_' + '_g';
  if (map.has(key)) {
    a = map.get(key);
  }
}

Library: None

The benchmark does not use any external libraries, which is good for isolating the test results and ensuring that the comparison between Map.get() and Map.has() + Map.get() is accurate.

Special JS Features or Syntax: None

There are no special JavaScript features or syntax used in this benchmark. The code uses standard JavaScript syntax and features to create the Map object, populate it with data, and measure performance.

Performance Comparison

The benchmark measures the execution rate of each test case using the ExecutionsPerSecond metric. This value represents the number of times each test case is executed per second on a given device.

In this benchmark, Mobile Safari 16 on an iPhone running iOS 16.4.1 achieved:

• Map get: 297.35552978515625 executions per second
• Map has get: 231.34327697753906 executions per second

These results indicate that Map.get() is slightly faster than Map.has() + Map.get().

Alternatives

Other alternatives for benchmarking JavaScript performance include:

1. Benchmarking libraries: Libraries like Benchmark.js, jsperf, or micro-benchmark provide more advanced features and control over the benchmarking process.
2. Testing frameworks: Frameworks like Jest, Mocha, or Cypress can be used to write and run tests, including performance benchmarks.
3. Browser-specific APIs: Some browsers, like Chrome, have APIs like performance.now() or PerformanceObserver that provide more accurate timing measurements.

Keep in mind that the choice of alternative depends on the specific use case, desired level of control, and performance requirements.