fix: Clone return time zone list to prevent the caller from modifying the cached value

Use getTime instead of valueOf for clarity.

Author: prantlf

perf/getZonedTime.perf.js

@@ -1,7 +1,7 @@
 const createSuite = require('./createSuite')
 const { findTimeZone, getZonedTime } = require('../dist')
 
-const unixTime = new Date(2018, 9, 1, 18, 1, 36, 386).valueOf()
+const unixTime = new Date(2018, 9, 1, 18, 1, 36, 386).getTime()
 const berlin = findTimeZone('Europe/Berlin')
 
 function getZonedTimeUsingDate () {

src/convert/convert.js

@@ -21,14 +21,14 @@ function attachEpoch (time, unixTime) {
 }
 
 function getUTCOffset (date, timeZone) {
-  const unixTime = typeof date === 'number' ? date : date.valueOf()
+  const unixTime = typeof date === 'number' ? date : date.getTime()
   const { abbreviation, offset } = getTransition(unixTime, timeZone)
   return { abbreviation, offset }
 }
 
 function getZonedTime (date, timeZone) {
   const gotUnixTime = typeof date === 'number'
-  const unixTime = gotUnixTime ? date : date.valueOf()
+  const unixTime = gotUnixTime ? date : date.getTime()
   const { abbreviation, offset } = getTransition(unixTime, timeZone)
   if (gotUnixTime || offset) {
     date = new Date(unixTime - offset * 60000)
@@ -99,7 +99,7 @@ function convertDateToTime (date) {
       : '???',
     offset: date.getTimezoneOffset()
   }
-  attachEpoch(time, date.valueOf())
+  attachEpoch(time, date.getTime())
   return time
 }
 

src/lookup/lookup.js

@@ -5,14 +5,14 @@ let names
 let links
 let instances
 
-function populateTimeZones (data) {
+function populateTimeZones ({ zones: zoneData, links: linkData }) {
   zones = {}
-  names = data.zones.map(packed => {
+  names = zoneData.map(packed => {
     const name = packed.substr(0, packed.indexOf('|'))
     zones[name] = packed
     return name
   })
-  links = data.links.reduce((result, packed) => {
+  links = linkData.reduce((result, packed) => {
     const [ name, alias ] = packed.split('|')
     result[alias] = name
     return result
@@ -21,7 +21,7 @@ function populateTimeZones (data) {
 }
 
 function listTimeZones () {
-  return names
+  return names.slice()
 }
 
 function findTimeZone (alias) {

test/convertDateToTime.test.js

@@ -19,7 +19,7 @@ it('converts a date to time', () => {
   expect(minutes).toEqual(30)
   expect(seconds).toEqual(15)
   expect(milliseconds).toEqual(234)
-  expect(epoch).toEqual(date.valueOf())
+  expect(epoch).toEqual(date.getTime())
   expect(typeof zone === 'object').toBeTruthy()
   const { abbreviation, offset } = zone
   expect(/\w+/.test(abbreviation)).toBeTruthy()

test/getZonedTime.test.js

@@ -33,7 +33,7 @@ it('converts the UNIX time to the correct time object', () => {
 
 it('recognizes daylight-saving time', () => {
   const unixTime = Date.UTC(2018, 6, 2, 9, 30, 15, 234)
-  const berlinTime = getZonedTime(unixTime.valueOf(), berlin)
+  const berlinTime = getZonedTime(unixTime, berlin)
   expect(typeof berlinTime === 'object').toBeTruthy()
   const { year, month, day, dayOfWeek, hours, minutes, seconds, milliseconds, zone, epoch } = berlinTime
   expect(year).toEqual(2018)