Benchmark: Map.get() !== undefined VS Map.has() + .get()

Map.get() !== undefined VS Map.has() + .get() (version: 1)

Performance comparison of Map.get() !== undefined to check if element exists and Map.has() as most of the time you need the element after the .has() check anyway. LIMITATION: The checks are not completely the same. If the map contains a key whose value is intentionally set to undefined (Map.set(1, undefined)), .has() will return true, while the .get() !== undefined will be false.

Comparing performance of: Map.get() !== undefined vs Map.has() + .get()

Created: 9 months ago by: Guest

Jump to the latest result

Script Preparation code:

var i = 0,
    count = 1000,
    a;
var map = new Map();

for (i = 0; i < count; i++) {
    if (Math.random() > 0.5) {
        map.set(i, i * i);
    }
}

Tests:

Map.get() !== undefined
for (i = 0; i < count; i++) { const v = map.get(i); if (v !== undefined) { a = v; } }
Map.has() + .get()
for (i = 0; i < count; i++) { if (map.has(i)) { a = map.get(i); } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map.get() !== undefined
Map.has() + .get()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0

Browser/OS: Firefox 140 on Linux

View result in a separate tab

Test name	Executions per second
Map.get() !== undefined	94123.2 Ops/sec
Map.has() + .get()	73214.4 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 9 months ago):

LLMs can make mistakes. Check important info.

The provided benchmark is a performance comparison between two methods for checking the existence of a key in a JavaScript `Map`—specifically, `Map.get() !== undefined` versus using `Map.has()` followed by `Map.get()`. Here's a breakdown of what each method entails, their pros and cons, and other important considerations.

### Methods Compared

1. **Map.get() !== undefined**
   - **Benchmark Definition**: This method retrieves the value associated with a key using `map.get(i)`. It then checks if the value is not `undefined`. 
   - **Pros**:
     - Simplicity: It uses a single method to check for existence and get the value in one step.
     - Fewer method calls: Since it integrates the checking and getting into one line, it can be more concise.
   - **Cons**:
     - False negatives: If a key exists but its corresponding value is explicitly `undefined` (e.g., `map.set(1, undefined)`), this check will return `false`, even though the key exists.
     - Lack of clarity in intent: Other developers may expect that `undefined` means the key does not exist, which can lead to ambiguity.

2. **Map.has() + .get()**
   - **Benchmark Definition**: This approach first checks for the presence of a key using `map.has(i)` and, if true, retrieves its value with `map.get(i)`.
   - **Pros**:
     - Accurate existence check: `map.has()` will return `true` even for keys with values that are `undefined`, ensuring no key is overlooked.
     - Clarity: The intent is clear—first, check for existence and then get the value, making it easier to read and understand.
   - **Cons**:
     - Slightly more overhead: This method involves two method calls, which can add a small amount of performance cost in scenarios with many checks.
     - Potential redundancy: If you're always going to use the value after checking its existence, making two calls can be considered inefficient.

### Benchmark Results

The latest benchmark results show:
- `Map.get() !== undefined` had approximately **94,123 executions per second**.
- `Map.has() + .get()` had around **73,214 executions per second**.

These results indicate that the simpler approach (`Map.get() !== undefined`) performed better in this specific benchmark. However, the context of your application matters: if you expect to have `undefined` values for keys, it's recommended to use `Map.has()` for clarity and correctness.

### Other Considerations

- **Use Cases**: Select the method best suited to your specific application needs. If performance is critical and undefined values are not a concern, the former method might be preferred. However, if you expect to handle undefined values or if code readability is a priority, the latter may be better.
  
- **Alternatives**: Depending on application needs, consider:
  - **Using Objects**: In some cases, a plain JavaScript object may suffice for key-value storage. However, there are limitations in terms of key types (only strings or symbols allowed). 
  - **WeakMap**: If memory efficiency is a concern, especially with frequently created and disposed objects, `WeakMap` might be an alternative, though it lacks the same features as `Map`.

In conclusion, while the benchmark shows performance differences, the choice between these methods should consider both performance and the significance of context in your specific use case.

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