performance-now

What is performance-now?

The performance-now npm package provides a high-resolution timestamp, similar to what you would get from performance.now() in a web browser. This is particularly useful for accurately measuring execution times in Node.js applications, where such precision is necessary for performance analysis and optimization.

What are performance-now's main functionalities?

High-resolution timing

This feature allows you to measure the time it takes to execute operations with high precision. The code sample demonstrates how to use performance-now to calculate the execution time of some operations in milliseconds.

const now = require('performance-now');
let start = now();
// Some time-consuming operations
let end = now();
console.log(`Execution time: ${end - start} milliseconds`);

Other packages similar to performance-now

date-now

Provides a shim for Date.now(). While it offers functionality to get the current timestamp, it does not offer the high-resolution timing that performance-now does, making it less suitable for precise performance measurements.

hrtime

This package is a polyfill for process.hrtime. It offers high-resolution time measurements similar to performance-now but is specifically designed to mimic Node.js's process.hrtime() method, making it more suitable for applications that rely on process.hrtime() for compatibility reasons.

nano-time

Offers high-resolution timestamps in nanoseconds. While it provides similar functionality to performance-now in terms of high-resolution timing, nano-time focuses on nanosecond precision, which can be more than what is needed for most performance measurement scenarios.

README

performance-now

Implements a function similar to performance.now (based on process.hrtime).

Modern browsers have a window.performance object with - among others - a now method which gives time in miliseconds, but with sub-milisecond precision. This module offers the same function based on the Node.js native process.hrtime function.

According to the High Resolution Time specification, the number of miliseconds reported by performance.now should be relative to the value of performance.timing.navigationStart. For this module, it's relative to when the time when this module got loaded. Right after requiring this module for the first time, the reported time is expected to have a near-zero value.

Using process.hrtime means that the reported time will be monotonically increasing, and not subject to clock-drift.

Example usage

var now = require("performance-now")
var start = now()
var end = now()
console.log(start.toFixed(3)) // ~ 0.05 on my system
console.log((start-end).toFixed(3)) // ~ 0.002 on my system

Running the now function two times right after each other yields a time difference of a few microseconds. Given this overhead, I think it's best to assume that the precision of intervals computed with this method is not higher than 10 microseconds, if you don't know the exact overhead on your own system.

Credits

The initial structure of this module was generated by Jumpstart, using the Jumpstart Black Coffee template.

License

performance-now is released under the MIT License.
Copyright (c) 2013 Meryn Stol