Benchmark: Testing for false vs === undefined for undefined member

Tests:

test truth
var n = {}; while(true) { if(!n.foo) break; }
test undefined
var n = {}; while(true) { if(n.foo===undefined) break; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
test truth
test undefined

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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I'll break down the provided benchmark and explain what's being tested, compared, and analyzed.

**Benchmark Overview**

The MeasureThat.net website provides a platform for creating and running JavaScript microbenchmarks. The current benchmark tests two approaches: using `=== undefined` to check if an object property exists (`test truth`) and using a logical test (`!n.foo)` to achieve the same result (`test undefined`).

**What's being tested?**

The primary objective of this benchmark is to determine whether there's a performance difference between these two approaches. The test focuses on the execution speed of the JavaScript engine in each browser.

**Options compared**

Two options are being compared:

1. **Using `=== undefined`**: This approach checks if the property exists using the strict equality operator (`===`). If the property is not present, it returns `true`.
2. **Using a logical test (`!n.foo)`**: This approach uses a negation operation to check if the property exists. If the property is not present, the negated value will be evaluated as `true`.

**Pros and Cons of each approach**

1. **Using `=== undefined`**:
	* Pros: This approach is more explicit and readable, making it easier for developers to understand the intent behind the code.
	* Cons: It may lead to slightly slower execution speeds due to the additional comparison operation.
2. **Using a logical test (`!n.foo)`**:
	* Pros: This approach can be faster because it uses a single negation operation instead of an equality check.
	* Cons: The code becomes less readable and more prone to errors, as the intent behind the code is not immediately clear.

**Library usage**

There is no library explicitly mentioned in the benchmark definition. However, the use of JavaScript's built-in object property access syntax (`n.foo`) relies on the ECMAScript standard, which specifies how objects are accessed and manipulated.

**Special JS feature or syntax**

The `=== undefined` approach uses a unique syntax that leverages JavaScript's type coercion rules to compare an object property with `undefined`. This is a subtle aspect of JavaScript that can affect performance in certain scenarios. The use of the logical test (`!n.foo)`) avoids this specific behavior, but may lead to other performance differences.

**Other alternatives**

In general, there are alternative approaches to check if an object property exists:

1. **Using `in` operator**: `if ('foo' in n)` or `if (n.hasOwnProperty('foo'))`
2. **Using bracket notation**: `n['foo'] !== undefined`
3. **Using a library function**: Some libraries, like Lodash, provide utility functions for checking object property existence.

It's worth noting that the choice of approach depends on the specific use case and personal preference. The MeasureThat.net benchmark aims to provide insight into performance differences between these approaches, but in many cases, readability and maintainability take precedence over potential performance optimizations.

Related benchmarks:

Testing for false vs === undefined for undefined member (version: 0)

Is there a performance benefit to replacing === undefined with a logical test?

Comparing performance of: test truth vs test undefined

Created: 8 years ago by: Guest

Jump to the latest result

test truth

test undefined

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):