Make user input interpretation more forgiving

index.html

@@ -94,6 +94,24 @@
         return Math.floor(Math.random() * (max - min + 1) + min);
     }
 
+    /**
+     * Given an expected value and an actual value, interprets the actual value as a weekday and returns `null` if they
+     * are equal; returns an empty string if they are not equal; and returns an error message otherwise.
+     *
+     * @param expected the weekday that `actual` should be equal to
+     * @param actual the weekday to compare to `expected`
+     */
+    function compareWeekdays(expected, actual) {
+        switch (DoomsdayDate.expandDayString(actual)) {
+            case expected:
+                return null;
+            case undefined:
+                return "Unrecognized day of week";
+            default:
+                return "";
+        }
+    }
+
 
     /**
      * An input that can be validated.
@@ -228,10 +246,10 @@
 
 
         /**
-         * Returns the first year of this `DoomsdayDate`'s century.
+         * Returns the number of this `DoomsdayDate`'s century.
          */
         getCentury() {
-            return Math.floor(this.date.getFullYear() / 100) * 100;
+            return Math.floor(this.date.getFullYear() / 100);
         }
 
         /**
@@ -284,6 +302,33 @@
             }
         };
 
+        /**
+         * Returns the day of the week corresponding to the given string.
+         *
+         * This is a convenience method for interpreting (incomplete) user inputs.
+         *
+         * @param dayString the day of the week to expand
+         */
+        static expandDayString(dayString) {
+            dayString = dayString.toLowerCase();
+            if (dayString.startsWith("m"))
+                return "Monday";
+            else if (dayString.startsWith("tu"))
+                return "Tuesday";
+            else if (dayString.startsWith("w"))
+                return "Wednesday";
+            else if (dayString.startsWith("th"))
+                return "Thursday";
+            else if (dayString.startsWith("f"))
+                return "Friday";
+            else if (dayString.startsWith("sa"))
+                return "Saturday";
+            else if (dayString.startsWith("su"))
+                return "Sunday";
+            else
+                return undefined;
+        }
+
         /**
          * Returns a random date in the range `0001-01-01` (inclusive) to `9999-12-31` (inclusive), wrapped inside a
          * `DoomsdayDate` object.
@@ -302,10 +347,11 @@
 
         const centuryInput = new class extends ValidatableInput {
             validate(value) {
-                return value === quizDate.getCenturyAnchorString() ? null : "";
+                return compareWeekdays(quizDate.getCenturyAnchorString(), value);
             }
 
             onValidInput() {
+                this.input.value = DoomsdayDate.expandDayString(this.input.value);
                 yearInput.selectInput();
             }
 
@@ -314,15 +360,16 @@
             }
 
             updateTitle() {
-                this.titleLabel.innerText = `Anchor day of century starting in ${quizDate.getCentury()}?`;
+                this.titleLabel.innerText = `Anchor day of century starting in ${quizDate.getCentury() * 100}?`;
             }
         }($("#century-input"), $("#century-title-label"), $("#century-error-label"));
         const yearInput = new class extends ValidatableInput {
             validate(value) {
-                return value === quizDate.getYearAnchorString() ? null : "";
+                return compareWeekdays(quizDate.getYearAnchorString(), value);
             }
 
             onValidInput() {
+                this.input.value = DoomsdayDate.expandDayString(this.input.value);
                 dayInput.selectInput();
             }
 
@@ -336,10 +383,11 @@
         }($("#year-input"), $("#year-title-label"), $("#year-error-label"));
         const dayInput = new class extends ValidatableInput {
             validate(value) {
-                return value === quizDate.getWeekdayString() ? null : "";
+                return compareWeekdays(quizDate.getWeekdayString(), value);
             }
 
             onValidInput() {
+                this.input.value = DoomsdayDate.expandDayString(this.input.value);
                 reloadQuiz();
             }