Inject moment as a dependency, avoid mutation of moment instance

[timoxley]

Current implementation breaks node's module system by mutating the global instance of moment. i.e. if two packages depend on different versions of moment-precise-range, which version is used? It will depend on the order they're loaded, which could change at runtime.

Secondly, users should have precise control over which version of moment they want/need to use.

Ideally, user passes moment into this plugin like so:

var moment = require('moment')
moment = require('moment-precise-range')(moment)

This removes need for moment-precise-range to even list moment as a dependency (I'd set it as a devDependency though so it's available during testing).

The plugin should not mutate the original moment instance. This means not using the official, yet destructive moment.fn method. Rather, the plugin would do something like this:

module.exports = function(moment) {
   moment = Object.create(moment) // protect original moment from modification
   moment.preciseDiff = preciseDiff
   return moment
}

Alternatively you could export the preciseDiff function in isolation so users can attach it to moment however they wish.

[timoxley]

Another alternative which doesn't attach anything to moment, just takes a moment instances and passes back a function bound to that instance:

module.exports = function(moment) {
  return function preciseDiff(d1, d2, opts) {
    // etc
  }
}

[timoxley]

Oh, my bad the Object.create suggestion won't work with moment because it's default export is a function. You can set the prototype directly on the function though, something like this:

module.exports = function(moment) {
  // protect original moment from modification
  var wrappedMoment = function() {
    return moment.apply(this, arguments)
  }
  wrappedMoment.__proto__ = moment
  wrappedMoment.preciseDiff = preciseDiff
  return wrappedMoment
}

[mtscout6]

I like where you are going with this. I don't have the time to address it right now, however I do take pull requests.

[psulek]

@mtscout6 just created pull #5