Benchmark: conditional self-assignment vs. membership check with in vs. membership check with hasOwnProperty

Script Preparation code:

var x = {
    foo: []
};
var keys = Array.from({
    length: 5000
}).map((x, i) => i < 2500 ? i : i - 2500);

Tests:

hasOwnProperty membership check
for (const key of keys) { if (!Object.prototype.hasOwnProperty.call(x, key)) { x[key] = []; } }
self-assignment
for (const key of keys) { x[key] = x[key] ?? []; }
in membership check
for (const key of keys) { if (!(key in x)) { x[key] = []; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
hasOwnProperty membership check
self-assignment
in membership check

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's break down the benchmark test.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark that tests three different approaches to assigning values to properties in an object:

1. `hasOwnProperty membership check` (using `in` operator)
2. `self-assignment` (using the nullish coalescing operator `??`)
3. `membership check with hasOwnProperty` (checking if the property is present using `hasOwnProperty` method)

**Options compared**

The benchmark compares these three approaches to assign values to properties in an object, specifically when trying to access a non-existent property.

**Pros and Cons of each approach:**

1. **`hasOwnProperty membership check`**:
	* Pros: Simple and readable code.
	* Cons: May be slower due to the overhead of calling `hasOwnProperty`, especially if the object is large or the property name is complex.
2. **`self-assignment`**:
	* Pros: Shorter and more concise code, which might lead to faster execution due to less overhead.
	* Cons: Requires understanding of the nullish coalescing operator (`??`) and its behavior with undefined values.
3. **`membership check with hasOwnProperty`**:
	* Pros: Similar to `hasOwnProperty membership check`, but using a method call, which might be slower than direct property access.
	* Cons: May require more overhead due to the method call, especially if the object is large.

**Library and purpose**

There are no libraries explicitly mentioned in the benchmark test. However, some JavaScript features used here:

* `Array.from()` is a built-in method for creating an array from an iterable.
* The nullish coalescing operator (`??`) is a relatively new feature introduced in ECMAScript 2020 (ES10).
* `hasOwnProperty` is a method on the `Object` prototype, which checks if a property exists on an object.

**Special JS features**

The benchmark uses the nullish coalescing operator (`??`), which was mentioned earlier. This operator allows you to provide a default value for a variable or expression that might be undefined or null.

**Other alternatives**

In addition to these three approaches, there are other ways to achieve similar results:

* Direct property access: `x[key] = []`
* Using a try-catch block with `try { x[key] } catch (e) {}` (not included in the benchmark test)
* Using a library like Lodash's `get` method (not mentioned here)

It's worth noting that the choice of approach depends on the specific use case and performance requirements.

Related benchmarks:

conditional self-assignment vs. membership check with in vs. membership check with hasOwnProperty (version: 0)

Comparing performance of: hasOwnProperty membership check vs self-assignment vs in membership check

Created: 2 years ago by: Guest

Jump to the latest result

hasOwnProperty membership check

self-assignment

in membership check

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):