Benchmark: new Date(Date.now()).toISOString() vs (Date.now()).toISOString()

Script Preparation code:


function toISOString() {
	return new Date().toISOString();
}

function nowToISOString() {
 	return new Date(Date.now()).toISOString()
}

Tests:

toISOString
for (var i=0; i<1000; ++i) { toISOString(); }
now
for (var i=0; i<1000; ++i) { nowToISOString(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
toISOString
now

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.212 Safari/537.36

Browser/OS: Chrome 90 on Windows

View result in a separate tab

Test name	Executions per second
toISOString	951.4 Ops/sec
now	828.7 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in the provided benchmark.

**Benchmark Purpose:**
The benchmark compares two approaches for converting JavaScript numbers to ISO strings:

1. `toISOString()`: This is a built-in JavaScript method that converts a date object to an ISO string, which includes the timestamp.
2. `nowToISOString()`: This function combines calling `Date.now()` (which returns the current timestamp as a number) and then passing the result to the `toISOString()` method.

**Options Compared:**
The benchmark is testing the performance difference between these two approaches. The test cases are:

* `toISOString`: A single call to `toISOString()` on an unspecified date object.
* `nowToISOString`: A loop that calls `nowToISOString()` 1000 times, which involves calling `Date.now()` and then `toISOString()`

**Pros and Cons of Approaches:**

1. `toISOString()`:
	* Pros: This approach is concise and direct. It's likely to be faster since it only involves a single method call.
	* Cons: This approach might be slower if the date object needs to be converted from a string or another format, as `toISOString()` has additional parsing and formatting steps.
2. `nowToISOString`:
	* Pros: This approach avoids any potential parsing or formatting issues with `toISOString()`, making it more robust. It's also easier to understand for developers who are familiar with `Date.now()`.
	* Cons: This approach involves an extra function call, which can introduce overhead due to the function call and parameter passing.

**Library/Function Used:**
There is no external library being used in this benchmark. However, it does rely on built-in JavaScript functions like `toISOString()` and `Date.now()`.

**Special JS Features/Syntax:**
The benchmark uses a feature of modern JavaScript called "var" declarations with the "hoisting" behavior, which can lead to unexpected results if not properly understood. The use of `++i` in the loop also involves incrementing an unsigned integer variable, which can be a source of bugs in certain environments.

**Other Alternatives:**
To achieve similar performance measurements, you could consider using other benchmarking tools like:

* V8 Benchmark Suite (specifically designed for Chrome and Node.js)
* Browserbench
* JSTestdriver
* jsPerf

Keep in mind that each tool has its strengths and weaknesses, and some might be more suitable for your specific use case than others.

If you were to rewrite the benchmark using a modern JavaScript syntax and idioms, it would look something like this:

```javascript
for (let i = 0; i < 1000; i++) {
  globalThis Date.now().toISOString();
}

for (let i = 0; i < 1000; i++) {
  Date.now().toISOString();
}
```

Or, using modern JavaScript with arrow functions and template literals:

```javascript
for (let i = 0; i < 1000; i++) {
  globalThis.Date.now().toISOString();
}

for (let i = 0; i < 1000; i++) {
  Date.now().toISOString();
}
```

These examples would be more suitable for modern JavaScript environments and might give you different results than the original benchmark.

Related benchmarks:

new Date(Date.now()).toISOString() vs (Date.now()).toISOString() (version: 0)

Comparing performance of: toISOString vs now

Created: 3 years ago by: Guest

Jump to the latest result

toISOString

now

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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