Benchmark: String typeof in High Frequency

Script Preparation code:

const strings = [];

for (let i = 0; i < 5000; ++i) {
  const randomString = (Math.random() * 100000).toString();
  strings.push(randomString);
}

window.strings = strings;

Tests:

Call typeof every time
window.strings.forEach(string => { if (typeof string === 'string') { const newString = string.substr(0, 250000); } });
Method Detect
window.strings.forEach(string => { if (string && string.substr) { const newString = string.substr(0, 250000); } });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Call typeof every time
Method Detect

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down what is being tested in the provided JSON benchmark.

**What is being tested?**

The test is comparing two approaches to determine if a string is of type 'string':

1. `typeof string === 'string'`
2. `string && string.substr`

These approaches are used in a JavaScript microbenchmarking context, where the goal is to measure which approach is faster.

**Options being compared:**

* `typeof string === 'string'`: This checks if the variable `string` is of type 'string'. It's a simple and straightforward way to check the type of a value.
* `string && string.substr`: This uses the "and" operator (`&&`) to check two conditions:
	+ Does `string` exist (i.e., is it not null or undefined)?
	+ If `string` exists, does it have a `substr` method?
	+ The `substr` method is then called on `string`.

**Pros and Cons of each approach:**

* `typeof string === 'string'`:
	+ Pros: Simple, easy to read, and understand. It's a built-in JavaScript operator.
	+ Cons: Can be slower because it involves a lookup in the `String.prototype` object.
* `string && string.substr`:
	+ Pros: Avoids the potential overhead of looking up `String.prototype` methods.
	+ Cons: Requires checking for existence and method presence, which can add overhead. It's also more verbose.

**Library used:**

In this benchmark, no specific library is required or used beyond the built-in JavaScript operators (`typeof`, `&&`, `substr`). However, if you were to use a library like Lodash or Underscore.js to provide utility functions (e.g., `_.isString`), it could potentially affect the results.

**Special JS feature/syntax:**

None of the approaches mentioned rely on any special JavaScript features or syntax beyond basic JavaScript language elements. However, some libraries might introduce additional complexity when used in conjunction with these tests.

**Alternative approaches:**

Other possible approaches to determine if a string is of type 'string' could include:

* Using `instanceof` operator (`string instanceof String`)
* Creating a custom function to check the type
* Using a third-party library like `is-string` or `type-check`

However, these alternatives might not provide any significant performance benefits over the two approaches being compared in this benchmark.

Overall, the choice between `typeof string === 'string'` and `string && string.substr` depends on your specific use case and priorities. If simplicity and readability are key, `typeof string === 'string'` might be a better choice. If you need to avoid potential overhead of `String.prototype` methods or prefer a more explicit check, `string && string.substr` could be the better option.

Related benchmarks:

String typeof in High Frequency (version: 0)

Comparing typeof vs method availability

Comparing performance of: Call typeof every time vs Method Detect

Created: 4 years ago by: Guest

Jump to the latest result

Call typeof every time

Method Detect

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):