Benchmark: obj[name] lookup perf

Script Preparation code:

var name  = 'f'
var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

undefined
undefined === obj[name];
typeof
!obj[name]
in
name in obj
hasOwnProperty
obj.hasOwnProperty(name);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty

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 provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark measures the performance of object lookup operations in JavaScript, specifically the `obj[name]` syntax. The script preparation code creates an object `obj` with multiple properties (`a`, `b`, `c`, `d`, and `e`), which are used as variables to test different aspects of the `obj[name]` expression.

**Options Compared**

The benchmark compares four different approaches:

1. `undefined === obj[name]`: This tests if the expression is true when `name` is undefined.
2. `!obj[name]`: This tests if the expression is false when `name` is not in the object's own properties.
3. `name in obj`: This tests if the expression is true when `name` is a property of the `obj` object (using the `in` operator).
4. `obj.hasOwnProperty(name)`: This tests if the expression is true when `name` is a property of the `obj` object that it owns directly, using the `hasOwnProperty` method.

**Pros and Cons**

Here are some pros and cons for each approach:

1. `undefined === obj[name]`:
	* Pros: Simple and straightforward.
	* Cons: May not accurately reflect real-world usage, as `name` is often used in a context where it's expected to be defined.
2. `!obj[name]`:
	* Pros: More accurate for determining if `name` is not in the object's own properties.
	* Cons: Uses the logical NOT operator (`!`) and may be less readable.
3. `name in obj`:
	* Pros: Elegant and concise way to check if a property exists in an object.
	* Cons: May return false positives if `name` is a property of another object (due to inheritance).
4. `obj.hasOwnProperty(name)`:
	* Pros: More precise control over what's considered a "own" property of the object.
	* Cons: May be less readable than using `in`.

**Special Considerations**

There are no special considerations or syntax-specific features mentioned in this benchmark.

**Alternatives**

If you were to rewrite this benchmark, you could consider alternative approaches, such as:

1. Using a more modern JavaScript feature like `optional chaining` (`?.`) or the new `has` method (`in` with an object).
2. Adding additional test cases to cover more edge cases (e.g., using a property name that's not a string, or testing for null or undefined values).

Keep in mind that the benchmark is focused on performance and simplicity, so any alternative approaches would need to balance these factors.

I hope this explanation helps you understand the benchmark!

Related benchmarks:

obj[name] lookup perf (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty

Created: 4 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

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):