Added support for the preferPast option

module/date-parser.js

@@ -40,14 +40,20 @@ export class DateParser {
 
     constructor(
         monthNames=DEFAULT_MONTH_NAMES,
-        shortMonthNames=DEFAULT_SHORT_MONTH_NAMES
+        shortMonthNames=DEFAULT_SHORT_MONTH_NAMES,
+        preferPast=false
     ) {
         // Set the month names used when formatting/parsing dates
         this.monthNames = monthNames
         this.shortMonthNames = shortMonthNames
+
+        // If `true` then the parser will prefer past dates when determining
+        // what century to generate (if not given).
+        this.preferPast = preferPast
     }
 
     // -- Getters & Setters ---
+
     get monthNames() {
         return this._monthNames.slice()
     }
@@ -79,6 +85,20 @@ export class DateParser {
         return this.constructor.formatters[formatter](this, date)
     }
 
+    /**
+     * Return a full year (4-digit) from a partial year (2-digit).
+     */
+    getFullYear(year) {
+        let currentYear = (new Date()).getYear()
+        let century = parseInt((new Date()).getFullYear() / 100, 10)
+
+        if (this.preferPast && (year + 100) > currentYear) {
+            century -= 1
+        }
+
+        return year + (century * 100)
+    }
+
     /**
      * Attempt to parse (and return) a string as a date using the list of
      * named parsers.
@@ -178,7 +198,7 @@ DateParser.parsers = {
         // If the year doesn't contain the century then we add the current
         // century to it.
         if (year < 100) {
-            year += parseInt((new Date()).getFullYear() / 100, 10) * 100
+            year = inst.getFullYear(year)
         }
 
         // Convert the components to a native date
@@ -298,7 +318,7 @@ DateParser.parsers = {
             // If the year doesn't contain the century then we add the current
             // century to it.
             if (year < 100) {
-                year += parseInt((new Date()).getFullYear() / 100, 10) * 100
+                year = inst.getFullYear(year)
             }
         }
 
@@ -379,7 +399,7 @@ DateParser.parsers = {
         // If the year doesn't contain the century then we add the current
         // century to it.
         if (year < 100) {
-            year += parseInt((new Date()).getFullYear() / 100, 10) * 100
+            year = inst.getFullYear(year)
         }
 
         // Convert the components to a native date

module/date-picker.js

@@ -71,6 +71,13 @@ export class DatePicker {
                  */
                 'parsers': ['human', 'dmy', 'iso'],
 
+                /**
+                 * A flag indicating that when the date parser automatically
+                 * generates a century for a date it should pick a century for
+                 * for past dates over future dates.
+                 */
+                'preferPast': false,
+
                 /**
                  * A list of abbreviated month names used by the date picker.
                  */
@@ -118,7 +125,8 @@ export class DatePicker {
         // parse options that contain dates).
         this._dateParser = new DateParser(
             this._options.monthNames,
-            this._options.shortMonthNames
+            this._options.shortMonthNames,
+            this._options.preferPast
         )
 
         // Handle date based options

package.json

@@ -1,6 +1,6 @@
 {
   "name": "manhattan-date-picker",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "Date parsing and picking for form fields.",
   "engines": {
     "node": ">=8.9.4"

spec/date-parser.spec.js

@@ -8,6 +8,28 @@ chai.should()
 chai.use(require('sinon-chai'))
 
 
+// Utils
+
+function freezeDate(d) {
+    Date._original = Date
+
+    class FrozenDate extends Date {
+        constructor() {
+            super()
+            return new Date._original(d)
+        }
+    }
+
+    global.Date = FrozenDate
+}
+
+function unfreezeDate() {
+    global.Date = Date._original
+}
+
+
+// Tests
+
 describe('DateParser', () => {
 
     describe('constructor', () => {
@@ -96,6 +118,10 @@ describe('DateParser', () => {
             parser = new DateParser()
         })
 
+        afterEach(() => {
+            parser = new DateParser()
+        })
+
         describe('format', () => {
             it('should format the given date using the named '
                 + 'formatter', () => {
@@ -106,6 +132,43 @@ describe('DateParser', () => {
             })
         })
 
+        describe('getFullYear (preferPast: false)', () => {
+
+            beforeEach(() => {
+                freezeDate(new Date(2020, 5, 11))
+            })
+
+            afterEach(() => {
+                unfreezeDate()
+            })
+
+            it('should return a full year for the current century', () => {
+                const y = parser.getFullYear(50)
+                y.should.equal(2050)
+            })
+        })
+
+        describe('getFullYear (preferPast: true)', () => {
+
+            beforeEach(() => {
+                freezeDate(new Date(2020, 5, 11))
+            })
+
+            afterEach(() => {
+                unfreezeDate()
+            })
+
+            it('should return a full year for the previous century', () => {
+                parser.preferPast = true
+
+                let y = parser.getFullYear(50)
+                y.should.equal(1950)
+
+                y = parser.getFullYear(10)
+                y.should.equal(2010)
+            })
+        })
+
         describe('parse', () => {
             it('should attempt to parse the given string using the list of '
                 + 'named parsers', () => {

spec/index.html

@@ -15,6 +15,7 @@
                 name="date"
                 value="11/06/2018"
                 data-mh-date-picker
+                data-mh-date-picker--prefer-past
                 >
         </label>