Benchmark: Undefined testing

Script Preparation code:

var x;
var y = {};

Tests:

typeof x === "undefined"
typeof x === "undefined"
x === undefined
x === undefined
x == undefined
x == undefined
x == null
x == null

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof x === "undefined"
x === undefined
x == undefined
x == null

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's break down the JavaScript microbenchmark provided by MeasureThat.net.

**Benchmark Definition**

The benchmark definition is a JSON object that represents the test case. In this case, there are four test cases:

1. `typeof x === "undefined"`
2. `x === undefined`
3. `x == undefined`
4. `x == null`

These test cases are essentially checking whether the variable `x` is equal to `undefined`, using different comparison operators (`===`, `==`, and `==`).

**Comparison Operators**

Let's examine each test case:

* `typeof x === "undefined"`: This test case checks if the type of `x` is `"undefined"`. Since `x` is declared as an empty object `{}`, its type is indeed `"object"`, not `"undefined"`.
* `x === undefined`: This test case checks if `x` is equal to `undefined`. In JavaScript, `undefined` and `null` are both primitive values, but `undefined` is the "default" value for uninitialized variables. Since `x` is declared as an empty object `{}`, it's not initialized with a value, so this test case should pass.
* `x == undefined`: This test case checks if `x` is equal to `undefined`. As mentioned earlier, since `x` is an uninitialized object `{}`, its primitive value (if any) would be an object type (`"[object Object]"`), not `undefined`. So, this test case should fail.
* `x == null`: This test case checks if `x` is equal to `null`. Since `x` is declared as an empty object `{}`, it's not explicitly set to `null`, so this test case should pass.

**Pros and Cons**

Here are some pros and cons of each approach:

* `typeof x === "undefined"`: Pros - It checks the type of `x` directly. Cons - Since `x` is an uninitialized object, its type is `"object"`, not `"undefined"`.
* `x === undefined`: Pros - This test case ensures that `x` has not been initialized with a value. Cons - It relies on JavaScript's "default" behavior for uninitialized variables.
* `x == undefined`: Pros - None. Cons - Since `x` is an uninitialized object, its primitive value would be an object type (`"[object Object]"`), making this test case unreliable.
* `x == null`: Pros - This test case ensures that `x` has been explicitly set to `null`. Cons - It's not a comprehensive check for all possible values of `x`.

**Library and Special JS Features**

None of these test cases rely on any specific JavaScript library or special features.

**Other Considerations**

When writing benchmarks, it's essential to consider the following:

* **Initialization**: Ensure that variables are properly initialized before running tests.
* **Type Coercion**: Be aware of type coercion rules in JavaScript, which can affect the results of your benchmark.
* **Primitive Values**: Understand how primitive values (e.g., `undefined`, `null`) behave in different contexts.

**Alternatives**

If you wanted to write similar benchmarks using a different approach:

1. Use `x = undefined` instead of `var x;` and `var y = {};`. This would ensure that `x` is explicitly initialized as `undefined`.
2. Use `Object.is(x, undefined)` or `x === Object.prototype.toString.call(x) === "undefined"` for a more explicit type check.
3. Use a different data structure (e.g., a primitive value like `NaN`) to test for specific values.

Keep in mind that MeasureThat.net's benchmarks are specifically designed to measure JavaScript execution performance, so it's essential to tailor your benchmarking approach to the specific requirements and characteristics of your codebase.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (iPad; CPU OS 15_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/112.0.5615.167 Mobile/15E148 Safari/604.1

Browser/OS: Chrome Mobile iOS 112 on iOS 15.6

View result in a separate tab

Test name	Executions per second
typeof x === "undefined"	14431740.0 Ops/sec
x === undefined	5395422.5 Ops/sec
x == undefined	5355203.5 Ops/sec
x == null	14574359.0 Ops/sec

Related benchmarks:

Undefined testing (version: 0)

Comparing performance of: typeof x === "undefined" vs x === undefined vs x == undefined vs x == null

Created: 7 years ago by: Guest

Jump to the latest result

typeof x === "undefined"

x === undefined

x == undefined

x == null

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):