Benchmark: Accessing a non-exist value

Script Preparation code:

var x = {
  existed: "value",
  nullVal: null,
}

Tests:

x.nonExist
const v = x.nonExist
x["nonExist"]
const v = x["nonExist"]
x.nullVal
const v = x.nullVal
x["nullVal"]
const v = x["nullVal"]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
x.nonExist
x["nonExist"]
x.nullVal
x["nullVal"]

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 microbenchmarking test case on the website MeasureThat.net. The benchmark measures the performance of accessing non-existent values in a JavaScript object.

**Script Preparation Code**

The script preparation code defines an object `x` with two properties: `existed` and `nullVal`. The property `nonExist` does not exist directly in the object, but is accessed through different methods:

* `const v = x.nonExist`: This method attempts to access a non-existent property directly.
* `const v = x[\"nonExist\"]`: This method accesses the non-existent property using bracket notation.
* `const v = x.nullVal`: This method accesses the `nullVal` property, which is defined and has a value.
* `const v = x[\"nullVal\"]`: This method accesses the `nullVal` property using bracket notation.

**Benchmark Comparison**

The benchmark compares the performance of accessing non-existent values using two different methods:

1. **Direct Property Access**: `const v = x.nonExist`
2. **Bracket Notation**: `const v = x[\"nonExist\"]`

**Pros and Cons**

* **Direct Property Access**: This method is simple and straightforward, but it may not be as efficient since the browser needs to perform a lookup in the object's prototype chain.
	+ Pros: Simple to implement, easy to understand.
	+ Cons: May be slower due to lookup in prototype chain.
* **Bracket Notation**: This method uses an array of strings to access the property, which may be more efficient since it avoids the lookup in the object's prototype chain.
	+ Pros: More efficient, reduces overhead by using an array.
	+ Cons: More complex to implement and understand.

**Library Considerations**

None of the benchmark tests use any external libraries or dependencies.

**Special JavaScript Features/Syntax**

None of the benchmark tests use any special JavaScript features or syntax beyond standard ECMAScript 2022 features.

**Alternative Approaches**

Other approaches to accessing non-existent values in a JavaScript object might include:

* Using `in` operator: `const v = x['nonExist']`
* Using `hasOwnProperty()` method: `if (x.hasOwnProperty('nonExist')) { const v = x.nonExist; } else { ... }`
* Using `Object.prototype.hasOwnProperty.call()` method: `if (Object.prototype.hasOwnProperty.call(x, 'nonExist')) { const v = x.nonExist; } else { ... }`

These approaches may have different performance characteristics and trade-offs in terms of complexity and readability.

Related benchmarks:

Accessing a non-exist value (version: 0)

Comparing performance of: x.nonExist vs x["nonExist"] vs x.nullVal vs x["nullVal"]

Created: 4 years ago by: Guest

Jump to the latest result

x.nonExist

x["nonExist"]

x.nullVal

x["nullVal"]

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):