Benchmark: Map .has() only vs .get() only

Script Preparation code:

function noop() {}
map = new Map();
keys = [];

for (let i = 0; i < 10000; i++) {
  const k = new Number(i);
  keys.push(k);
  if (k % 2 !== 0) map.set(k, i);
}

Tests:

.has()
keys.forEach(k=>{ if (map.has(k)) noop() })
.get() only
keys.forEach(k => { const v = map.get(k); if (v) noop(v); })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.has()
.get() only

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its options.

**What is being tested:**

The benchmark measures the performance difference between two approaches for checking if an element exists in a Map:

1. `map.has(key)`
2. `const v = map.get(key); if (v) func1(v);`

In both cases, we iterate over an array of 10,000 numbers and set some elements in the Map only when their index is odd.

**Options being compared:**

There are two test cases:

1. `.has()`: Uses `map.has(key)` to check if a key exists.
2. `.get() only`: Uses `const v = map.get(key); if (v) func1(v);` to get the value associated with the key and then checks if it's truthy.

**Pros and Cons of each approach:**

* `.has()`
	+ Pros:
		- More efficient, as it directly checks if the key exists without retrieving its value.
		- Faster lookup time, since `map.has()` is implemented in native code.
	+ Cons:
		- Does not provide any information about the existing value, so the function passed to `func1` will always be executed even if no value is set for that key.
* `.get() only`
	+ Pros:
		- Provides more information about the existing value (its actual value), but still executes the function with this value even if it's undefined or null.
	+ Cons:
		- Less efficient, since `map.get()` retrieves the associated value from memory.

**Library used:**

In both test cases, the Map data structure is provided by the JavaScript standard library. A Map is a collection of key-value pairs that can be iterated over using methods like `has()`, `get()`, and `forEach()`.

**Special JS feature or syntax not mentioned:**

The benchmark does not use any special JavaScript features or syntax beyond standard language constructs.

**Other alternatives:**

If you need to optimize the performance of your Map-based code, you might consider:

* Using a different data structure, like an Object or an array, depending on your specific requirements.
* Implementing custom optimizations for specific cases (e.g., caching frequently accessed keys).
* Profiling and analyzing your application's memory usage to identify potential bottlenecks.

Keep in mind that the best approach depends on the specifics of your use case and performance constraints.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.229 Whale/2.10.123.42 Safari/537.36

Browser/OS: Chrome 90 on Windows

View result in a separate tab

Test name	Executions per second
.has()	488.8 Ops/sec
.get() only	484.0 Ops/sec

Related benchmarks:

Map .has() only vs .get() only (version: 0)

This is to compare the cost of this pattern ```if (map.has(key)) ``` v/s ```const v = map.get(key); if (v) func1(v);```

Comparing performance of: .has() vs .get() only

Created: 3 years ago by: Guest

Jump to the latest result

.has()

.get() only

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):