Benchmark: instanceof vs tagname

HTML Preparation code:

<div><iframe></iframe></div>

Tests:

instanceof
const iframe = document.querySelector('iframe') if(iframe instanceof HTMLIFrameElement) console.log('hi');
tagName
const iframe = document.querySelector('iframe') if(iframe.tagName === 'IFRAME') console.log('hi');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
tagName

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	324283.4 Ops/sec
tagName	334762.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its test cases to understand what is being tested.

**Benchmark Overview**

The benchmark, named "instanceof vs tagname", compares two approaches to check if an element is of a specific type: `instanceof` and `tagName`. The goal is to determine which approach is faster.

**Options Compared**

Two options are compared:

1. **`instanceof`**: This method checks if the object is an instance of the specified class. It is typically used with classes, interfaces, or constructors.
2. **`tagName`**: This method compares the value of the `tagName` property of the element to a string literal.

**Pros and Cons**

*   **`instanceof`**: Pros:
    *   More precise and flexible, as it checks for any subclass or constructor inheritance.
    *   Can be used with classes, interfaces, or constructors.
    *   Often preferred by developers due to its precision and flexibility.
*   **`tagName`**: Pros:
    *   Simpler and faster, as it only compares the `tagName` property.
    *   Suitable for most use cases where you just need to identify an element based on its tag name.

Cons of `instanceof`:

*   May be slower due to the additional checks required to verify class inheritance.
*   Requires a more precise understanding of the classes or interfaces involved.

Cons of `tagName`:

*   Less flexible and less precise, as it only checks for exact matches with the specified tag name.
*   May not work correctly if the element's tagName is dynamically set or changed.

**Library and Special JS Features**

The benchmark uses no specific JavaScript library. However, it does use a special JavaScript feature called "template literals" (denoted by the backticks `` ` ``) in some of the test cases to compare strings.

**Other Considerations**

When choosing between `instanceof` and `tagName`, consider the following:

*   Use `instanceof` when you need to check for any subclass or constructor inheritance, such as with classes or interfaces.
*   Use `tagName` when you only need to identify an element based on its tag name, such as in simple DOM manipulation tasks.

**Other Alternatives**

Besides `instanceof` and `tagName`, other alternatives to check the type of an object in JavaScript include:

*   **`typeof`**: Returns a string indicating the type of the value. However, it has limitations, such as not supporting some advanced types (e.g., BigInt).
*   **`Object.prototype.toString()`**: Returns a string representation of the object's type. This method can be more informative than `typeof`, but it may still have limitations.
*   **Type checking libraries**: There are several third-party libraries available that provide more advanced and flexible type checking capabilities, such as TypeScript or type guards.

In summary, `instanceof` is generally preferred for its precision and flexibility, while `tagName` is simpler and faster but less precise. The choice ultimately depends on the specific requirements of your use case.

Related benchmarks:

instanceof vs tagname (version: 0)

Comparing performance of: instanceof vs tagName

Created: 4 years ago by: Guest

Jump to the latest result

instanceof

tagName

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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