performance-now

Implements performance.now (based on process.hrtime).

npm install performance-now
78 downloads in the last day
143 downloads in the last week
253 downloads in the last month

performance-now Build Status Dependency Status

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

npm loves you