Benchmark: is variable undefined? typeof variable === "undefined" vs variable === undefined

Tests:

typeof string is undefined
typeof "not undefined" === "undefined"
typeof undefined is undefined
typeof undefined === "undefined"
string is undefined
"not undefined" === undefined
undefined is undefined
undefined === undefined

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof string is undefined
typeof undefined is undefined
string is undefined
undefined is undefined

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
typeof string is undefined	235450816.0 Ops/sec
typeof undefined is undefined	224156416.0 Ops/sec
string is undefined	226660032.0 Ops/sec
undefined is undefined	243970304.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested on the provided JSON data.

The benchmark is testing two approaches for checking if a variable is undefined:

1. `typeof variable === "undefined"` (Method 1)
2. `variable === undefined` (Method 2)

**Options Comparison**

Both methods are used to check if a variable is undefined, but they differ in how the comparison is performed.

* **Method 1: `typeof variable === "undefined"`**
	+ This method uses the `typeof` operator to get the type of the variable.
	+ It then checks if the result is equal to `"undefined"`.
	+ This approach can be slower because it involves an additional operation (getting the type).
* **Method 2: `variable === undefined`**
	+ This method directly compares the variable with `undefined`.
	+ This approach is often faster because it's a simple equality check.

**Pros and Cons**

* **Method 1 (typeof)**:
	+ Pros: Can be useful in certain situations where you need to get the type of a variable before comparing it.
	+ Cons: Generally slower due to the additional operation.
* **Method 2 (direct comparison)**:
	+ Pros: Faster because it's a simple equality check.
	+ Cons: May not work correctly for all variables (e.g., if `undefined` is not a primitive value).

**Other Considerations**

Both methods can be affected by the type of variable being checked. For example:

* If the variable is an object, `typeof variable === "object"` might return `"object"`, rather than `"undefined"`.
* If the variable is set to `null`, both methods will return `false`.

**Library and Special JS Features**

None of the tests appear to use a specific library or special JavaScript features.

**Benchmark Preparation Code**

The preparation code for each test case is not provided, but it's likely that they involve setting up variables with different types (e.g., strings, numbers, undefined) and running the benchmark multiple times to get accurate results.

**Other Alternatives**

If you want to explore other approaches to checking if a variable is undefined, consider:

* Using `hasOwnProperty` on an object: `if (variable.hasOwnProperty("constructor")) { ... }`
* Using `instanceof`: `if (!(variable instanceof Object)) { ... }`
* Using a library like Lodash's `isUndefined` function

Keep in mind that these alternatives might not provide the same level of performance as Method 2, but they can offer more flexibility or correctness in certain situations.

Related benchmarks:

is variable undefined? typeof variable === "undefined" vs variable === undefined (version: 0)

Comparing whether checking is (typeof variable === "undefined") is faster than (variable === undefined)

Comparing performance of: typeof string is undefined vs typeof undefined is undefined vs string is undefined vs undefined is undefined

Created: 5 years ago by: Guest

Jump to the latest result

typeof string is undefined

typeof undefined is undefined

string is undefined

undefined is undefined

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):