Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
Implements a function similar to `performance.now` (based on `process.hrtime`).
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 milliseconds, but with sub-millisecond precision. This module offers the same function based on the Node.js native `process.hrtime` function.
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.
Using `process.hrtime` means that the reported time will be monotonically increasing, and not subject to clock-drift.
According to the [High Resolution Time specification](http://www.w3.org/TR/hr-time/), 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.
According to the [High Resolution Time specification](http://www.w3.org/TR/hr-time/), the number of milliseconds reported by `performance.now` should be relative to the value of `performance.timing.navigationStart`.
In the current version of the module (2.0) the reported time is relative to the time the current Node process has started (inferred from `process.uptime()`).
Version 1.0 reported a different time. The reported time was relative to the time the module was loaded (i.e. the time it was first `require`d). If you need this functionality, version 1.0 is still available on NPM.
Using `process.hrtime` means that the reported time will be monotonically increasing, and not subject to clock-drift.
## Example usage
## Example usage
...
@@ -18,13 +14,17 @@ Version 1.0 reported a different time. The reported time was relative to the tim
...
@@ -18,13 +14,17 @@ Version 1.0 reported a different time. The reported time was relative to the tim
varnow=require("performance-now")
varnow=require("performance-now")
varstart=now()
varstart=now()
varend=now()
varend=now()
console.log(start.toFixed(3))// the number of milliseconds the current node process is running
console.log(start.toFixed(3))// ~ 0.05 on my system
console.log((start-end).toFixed(3))// ~ 0.002 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.
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](https://github.com/meryn/jumpstart), using the [Jumpstart Black Coffee](https://github.com/meryn/jumpstart-black-coffee) template.
## License
## License
performance-now is released under the [MIT License](http://opensource.org/licenses/MIT).
performance-now is released under the [MIT License](http://opensource.org/licenses/MIT).
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
