Extracted from hour module

Author: ad-si

.gitignore

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+/build

.npmignore

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+/source

package.json

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+{
+  "name": "@datatypes/duration",
+  "version": "0.1.0",
+  "description": "Full ISO 8601 compatible duration class",
+  "main": "build/index.js",
+  "directories": {
+    "test": "test"
+  },
+  "scripts": {
+    "build": "babel --quiet --presets es2015 source --out-dir build",
+    "test": "npm run build && ava --fail-fast",
+    "prepublish": "npm test"
+  },
+  "keywords": [
+    "duration",
+    "iso 8601",
+    "date"
+  ],
+  "author": "Adrian Sieber",
+  "devDependencies": {
+    "ava": "^0.12.0",
+    "babel-cli": "^6.6.5",
+    "babel-preset-es2015": "^6.6.0",
+    "unexpected": "^10.4.0"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/datatypes/duration.git"
+  },
+  "bugs": {
+    "url": "https://github.com/datatypes/duration/issues"
+  },
+  "homepage": "https://github.com/datatypes/duration#readme",
+  "dependencies": {},
+  "license": "ISC"
+}

source/fragments.js

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+'use strict'
+
+export default [
+	'years',
+	'months',
+	'weeks',
+	'days',
+	'hours',
+	'minutes',
+	'seconds',
+	'milliseconds'
+]

source/index.js

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+import durationFragments from './fragments'
+
+export default class Duration {
+	constructor (durationString) {
+		let durationPattern =
+			'P' +
+			'(?:(\\d+)Y)?' + // Years
+			'(?:(\\d+)M)?' + // Months
+			'(?:(\\d+)W)?' + // Weeks
+			'(?:(\\d+)D)?' + // Days
+			'T?' +
+			'(?:(\\d+)H)?' + // Hours
+			'(?:(\\d+)M)?' + // Minutes
+			'(?:(\\d+)?' +   // Seconds
+			'\\.?(\\d+)?S)?' // Milliseconds
+
+		let regex = new RegExp(durationPattern, 'i')
+		let durationArray = durationString.match(regex)
+
+		durationFragments.forEach((fragment, index) => {
+			let value = Number(durationArray[index + 1])
+			if (value)
+				this[fragment] = value
+		})
+	}
+
+	get string () {
+		return durationFragments
+			.reduce(
+				(string, fragment) => {
+					if (this[fragment] == null) {
+						return string
+					}
+
+					if (fragment === 'minutes' && !string.includes('t')) {
+						string += 't'
+					}
+
+					string += this[fragment] + fragment.substr(0, 1)
+
+					if (fragment === 'days') {
+						string += 't'
+					}
+					if (fragment === 'milliseconds') {
+						string.replace('s', '.' + this[fragment] + 's')
+					}
+
+					return string
+				},
+				'p'
+			)
+			.replace(/t$/, '')
+			.toUpperCase()
+	}
+
+	toString () {
+		return this.string
+	}
+
+	toObject () {
+		return durationFragments.reduce(
+			(object, fragment) => {
+				if (this[fragment] != null)
+					object[fragment] = this[fragment]
+				return object
+			},
+			{
+				string: this.string
+			}
+		)
+	}
+
+	toJSON () {
+		return this.toObject()
+	}
+}

test/main.js

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+import runTest from 'ava'
+import expect from 'unexpected'
+import Duration from '../build/index.js'
+
+runTest('P7Y', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			years: 7,
+		}
+	)
+})
+
+runTest('P7M', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			months: 7,
+		}
+	)
+})
+
+runTest('P7W', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			weeks: 7,
+		}
+	)
+})
+
+runTest('P7D', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			days: 7,
+		}
+	)
+})
+
+runTest('P7H', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			hours: 7,
+		}
+	)
+})
+
+runTest('PT7M', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			minutes: 7,
+		}
+	)
+})
+
+runTest('P7S', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			seconds: 7,
+		}
+	)
+})
+
+runTest('P7.345S', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: 'P7S345M',
+			seconds: 7,
+			milliseconds: 345,
+		}
+	)
+})
+
+runTest('P7Y5M', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			years: 7,
+			months: 5
+		}
+	)
+})
+
+runTest('P3Y6M4DT12H30M5S', test => {
+	expect(
+		new Duration(test.title).toObject(),
+		'to equal',
+		{
+			string: test.title,
+			years: 3,
+			months: 6,
+			days: 4,
+			hours: 12,
+			minutes: 30,
+			seconds: 5,
+		}
+	)
+})