Benchmark: typeof vs comparison

Script Preparation code:

var variable = undefined;

Tests:

Typeof
if (typeof variable === 'undefined') { console.log('typeof'); }
Comparison
if (variable === undefined) { console.log('comparison'); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Typeof
Comparison

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):

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Let's break down the provided JSON and explain what's being tested.

**Benchmark Definition**

The benchmark is comparing two approaches to check if a variable is undefined:

1. `typeof` operator: This checks the type of the variable using the `typeof` operator. In JavaScript, `undefined` is not equal to `undefined`, but rather is considered a distinct type.
2. Direct comparison (`===`): This directly compares the value of the variable with `undefined`.

**Options Compared**

The two options being compared are:

* Using the `typeof` operator to check if a variable is undefined
* Directly comparing the variable's value with `undefined`

**Pros and Cons**

* **Using `typeof` operator:**
	+ Pros:
		- More intuitive for developers, as it clearly indicates that the type of the variable is being checked.
		- Less prone to errors, as it avoids direct equality checks.
	+ Cons:
		- Performance overhead, as it involves a type check and potentially additional memory allocation.
		- May not be as efficient on modern JavaScript engines that optimize `typeof` behavior.
* **Direct comparison (`===`):**
	+ Pros:
		- More straightforward and efficient, as it simply compares the value with `undefined`.
		- Less overhead than using `typeof`.
	+ Cons:
		- Requires careful handling of cases where the variable might be an object or have a custom `valueOf()` method.
		- May lead to errors if not handled correctly.

**Library and Special JS Features**

None mentioned in this specific benchmark. However, some libraries like Lodash or others might provide additional functions for working with undefined values.

**Special JS Features**

The only special feature that comes into play here is the behavior of `typeof` operator when checking for `undefined`. It's worth noting that older versions of JavaScript (e.g., before ECMAScript 5) would return `'undefined'` instead of `'object'` when checking a variable with `typeof`.

**Other Alternatives**

Some alternative approaches to check if a variable is undefined could include:

* Using the `in` operator: `variable in { }`
* Checking the `HasOwnProperty()` method: `variable.hasOwnProperty('')`
* Using a custom function or utility library

However, these alternatives might not be as efficient or straightforward as using `typeof` or direct comparison.

**Benchmark Preparation Code**

The provided script preparation code creates an undefined variable and assigns it to a local scope. This ensures that the variable is accessible only within the test case.

**Individual Test Cases**

Each test case runs the respective benchmark definition, logging either 'Typeof' or 'Comparison' to the console if the condition is met.

**Latest Benchmark Result**

The latest results show:

* For the `typeof` approach: 355991.9375 executions per second
* For the direct comparison (`===`) approach: 344776.6875 executions per second

This suggests that, on this specific test case, using the `typeof` operator leads to slightly better performance compared to direct comparison. However, please note that these results are likely to vary depending on the JavaScript engine, version, and other factors.

Related benchmarks:

typeof vs comparison (version: 0)

Comparing performance of: Typeof vs Comparison

Created: 3 years ago by: Registered User

Jump to the latest result

Typeof

Comparison

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):