Benchmark: key in object vs. object[key]

Script Preparation code:

var object = {a: 5, b: 6, c: 7};

Tests:

Using in keyword
"a" in object; "b" in object; "c" in object;
Using property access
!!object["a"]; !!object["b"]; !!object["c"];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using in keyword
Using property access

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark on the website MeasureThat.net. The benchmark tests two different approaches to accessing properties of an object: using the `in` keyword and property access.

**Test Case 1: "Using in keyword"**

This test case compares the performance of accessing properties using the `in` keyword, which checks if a property is present in an object (e.g., `"a" in object`). The test code:
```javascript
"a" in object;
"b" in object;
"c" in object;
```
**Pros and Cons**

* **Pros:**
	+ Easy to read and maintain: the syntax is straightforward, and it's easy to understand what's happening.
	+ Less error-prone: if you make a mistake with property names, the `in` keyword will help catch it.
* **Cons:**
	+ Potential performance overhead: since `in` checks for presence, it may involve additional operations or checks compared to direct property access.

**Test Case 2: "Using property access"**

This test case compares the performance of accessing properties directly using square brackets (e.g., `object["a"]`). The test code:
```javascript
!!object["a"];
!!object["b"];
!!object["c"];
```
**Pros and Cons**

* **Pros:**
	+ Faster execution: direct property access is typically faster since it doesn't involve an additional check.
	+ More efficient memory usage: no need to store intermediate results or perform unnecessary checks.
* **Cons:**
	+ Error-prone: if you make a mistake with property names, the code will throw a TypeError.

**Library and Special JS Features**

Neither of these test cases uses any libraries. However, they do utilize JavaScript's built-in `in` keyword, which is a standard feature in most modern JavaScript engines.

**Other Considerations**

* The benchmark measures the performance of accessing properties using both approaches on a fixed object (`object = {a: 5, b: 6, c: 7};`). This might not reflect real-world scenarios where objects are dynamically created or modified.
* The `!!` operator (double negation) is used to ensure strict equality checking. While this might be a good practice in some cases, it can also introduce unnecessary overhead.

**Alternatives**

If you wanted to benchmark accessing properties using other methods, here are some alternatives:

1. **Brackets with optional chaining**: Accessing properties using square brackets and the optional chaining operator (`?.`) might be another approach to explore:
```javascript
object?.["a"];
```
2. **Using `Object.hasOwn`**: This method checks if an object has a property without throwing an error if it doesn't exist:
```javascript
Object.hasOwn(object, "a");
```
3. **Using `in` with a custom implementation**: You could implement your own custom checking mechanism for property presence, but this would likely be slower and more complicated.

Keep in mind that these alternatives might not provide significant improvements or changes to the performance results compared to the original benchmark.

Related benchmarks:

key in object vs. object[key] (version: 0)

Comparing performance of: Using in keyword vs Using property access

Created: 5 years ago by: Guest

Jump to the latest result

Using in keyword

Using property access

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):