Benchmark: epoch milliseconds to ISO string, precalculated numbers 2

Script Preparation code:

var seed = Date.now();

var twoDigits = [];

for(let i = 0; i<100; i++) {
	twoDigits.push(String(i).padStart(2, '0'));
}

var threeDigits = [];

for(let i = 0; i<1000; i++) {
	threeDigits.push(String(i).padStart(3, '0'));
}

function toISO1(x) {
    Number.isFinite(x);

    const time = new Date(x);
    
    const year = String(time.getUTCFullYear());
    const mo = twoDigits[time.getUTCMonth()+1];
    const da = twoDigits[time.getUTCDate()];
    const ho = twoDigits[time.getUTCHours()];
    const mi = twoDigits[time.getUTCMinutes()];
    const se = twoDigits[time.getUTCSeconds()];
    const mil = threeDigits[time.getUTCMilliseconds()];
    
    return [year, '-', mo, '-', da, 'T', ho, ':', mi, ':', se, '.', mil, 'Z'].join('');
}

function toISO2(x) {
	return new Date(x).toISOString();
}

Tests:

template strings and padding
var value = toISO1(seed);
toISOString()
var value = toISO2(seed);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
template strings and padding
toISOString()

Fastest: N/A

Slowest: N/A

Latest run results:

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

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**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmarking test case, where users can create and run benchmarks to measure performance differences between various approaches. In this specific test case, we have two benchmark definitions: `toISO1` and `toISO2`, which are used to convert epoch time into an ISO string.

**What is being tested?**

The main goal of these benchmarks is to compare the performance of two different methods for converting epoch time into an ISO string:

1.  **Method 1 (`toISO1`)**: This method uses a custom implementation, where we create a Date object from the given epoch time and then manually construct the ISO string using template strings.
2.  **Method 2 (`toISO2`)**: This method leverages the built-in `toISOString()` function of JavaScript's built-in `Date` class.

**Options compared**

In this benchmark, we are comparing:

*   Method 1 (`toISO1`) with a custom implementation using template strings and manual string concatenation.
*   Method 2 (`toISO2`) with the built-in `toISOString()` function from the `Date` class.

**Pros and Cons of each approach:**

### **Method 1 (`toISO1`)**

Pros:

*   Control over every step of the conversion process, which might be beneficial in specific scenarios.
*   Can potentially provide insights into the performance of manual string manipulation compared to built-in functions.

Cons:

*   Manual string concatenation can lead to slower performance due to the overhead of creating and joining strings.
*   Error-prone code with a higher chance of bugs or inconsistencies.

### **Method 2 (`toISO2`)**

Pros:

*   Built-in function with optimized implementation, making it generally faster than manual approaches.
*   Less prone to errors since it's a well-established standard part of the JavaScript language.

Cons:

*   Less control over the conversion process compared to `toISO1`.
*   Might not be suitable for specific scenarios where custom formatting is required.

**Library and purpose**

In this benchmark, we use the built-in `Date` class in JavaScript. The `Date` class provides methods like `getUTCFullYear()`, `getUTCMonth()`, `getUTCDate()`, `getUTCHours()`, `getUTCMinutes()`, `getUTCSeconds()`, and `getUTCMilliseconds()` to access various parts of a date object.

**Special JavaScript feature or syntax**

In this benchmark, we are using template strings (e.g., `"year: ${time.getUTCFullYear()}, month: ${twoDigits[time.getUTCMonth()+1]}, ..."`). This is a modern JavaScript feature introduced in ECMAScript 2015 (ES6) that allows string interpolation.

**Alternatives**

Other alternatives to `toISO1` or `toISO2` could include:

*   Using the `Intl.DateTimeFormat()` API for formatting dates.
*   Leveraging libraries like Moment.js for date and time manipulation.
*   Employing other custom implementation methods, such as parsing and constructing strings from scratch.

However, these alternatives might introduce additional dependencies or complexity compared to the simple, built-in functions provided by JavaScript's `Date` class.

Related benchmarks:

epoch milliseconds to ISO string, precalculated numbers 2 (version: 0)

A function that converts an epoch time into an ISO string

Comparing performance of: template strings and padding vs toISOString()

Created: 5 years ago by: Guest

Jump to the latest result

template strings and padding

toISOString()

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):