Create classes to reduce duplication

index.html

@@ -22,6 +22,10 @@
             display: none;
         }
 
+        .error-message {
+            color: red;
+        }
+
         input[data-entered=true]:valid {
             background-color: green;
         }
@@ -52,26 +56,26 @@
         <form>
             <label for="century" id="century-label">Century</label>
             <input type="text" id="century" autocomplete="off" autofocus /> <!--list="weekdays"-->
-            <span class="invisible" id="century-error">Error message</span>
+            <span class="invisible error-message" id="century-error">Error message</span>
 
             <label for="year" id="year-label">Year</label>
             <input type="text" id="year" autocomplete="off" />
-            <span class="invisible" id="year-error">Error message</span>
+            <span class="invisible error-message" id="year-error">Error message</span>
 
             <label for="day" id="day-label">Day</label>
             <input type="text" id="day" autocomplete="off" />
-            <span class="invisible" id="day-error">Error message</span>
+            <span class="invisible error-message" id="day-error">Error message</span>
 
 
-<!--            <datalist id="weekdays">-->
+            <!--            <datalist id="weekdays">-->
-<!--                <option value="Monday">-->
+            <!--                <option value="Monday">-->
-<!--                <option value="Tuesday">-->
+            <!--                <option value="Tuesday">-->
-<!--                <option value="Wednesday">-->
+            <!--                <option value="Wednesday">-->
-<!--                <option value="Thursday">-->
+            <!--                <option value="Thursday">-->
-<!--                <option value="Friday">-->
+            <!--                <option value="Friday">-->
-<!--                <option value="Saturday">-->
+            <!--                <option value="Saturday">-->
-<!--                <option value="Sunday">-->
+            <!--                <option value="Sunday">-->
-<!--            </datalist>-->
+            <!--            </datalist>-->
         </form>
     </section>
 
@@ -91,121 +95,257 @@
 <!-- Scripts -->
 <script src="https://static.fwdekker.com/js/common.js" crossorigin="anonymous"></script>
 <script>
-    // rand in range [min, max] (both inclusive)
+    /**
-    const random = function (min, max) {
+     * Returns a number between `min` (inclusive) and `max` (inclusive).
+     *
+     * @param min the lower bound of permissible values
+     * @param max the upper bound of permissible values
+     */
+    function generateRandom(min, max) {
         return Math.floor((Math.random() * (max - min + 1)) + min);
-    };
+    }
 
-    // generate date in range [0001-01-01, 9999-12-31]
-    const generateDate = function () {
-        const minDate = new Date("0001-01-01").getTime() / 86400000;
-        const maxDate = new Date("9999-12-31").getTime() / 86400000;
-        return new Date(random(minDate, maxDate) * 86400000);
-    };
 
-    const dayNumberToWeekDay = function (dayNumber) {
+    /**
-        switch (dayNumber) {
+     * An element that can be validated.
-            case 0:
+     *
-                return "Sunday";
+     * In particular, the century, year, and day inputs of the Doomsday test.
-            case 1:
+     */
-                return "Monday";
+    class ValidatableElement {
-            case 2:
+        /**
-                return "Tuesday";
+         * Constructs a new validatable element and registers event listeners.
-            case 3:
+         *
-                return "Wednesday";
+         * @param element the element that is validatable
-            case 4:
+         * @param titleLabel the label with the `labelFor` property for the element given as the first parameter
-                return "Thursday";
+         * @param errorLabel the label to display errors in
-            case 5:
+         */
-                return "Friday";
+        constructor(element, titleLabel, errorLabel) {
-            case 6:
+            this.element = element;
-                return "Saturday";
+            this.titleLabel = titleLabel;
+            this.errorLabel = errorLabel;
+
+            this.element.addEventListener("keydown", event => {
+                if (event.key !== "Enter")
+                    return;
+
+                this.element.dataset["entered"] = "true";
+
+                const errorMessage = this.validate(this.element.value);
+                this.element.setCustomValidity(errorMessage || "");
+                this.errorLabel.innerText = errorMessage || "";
+                if (errorMessage === null) {
+                    this.errorLabel.classList.add("invisible");
+                    this.onValidInput();
+                } else {
+                    this.errorLabel.classList.remove("invisible");
+                    this.element.select();
+                    this.onInvalidInput();
+                }
+            });
         }
-    };
-
-    const centuryToAnchor = function (century) { // century is e.g. 1900 or 19, doesn't really matter since it's mod
-        return dayNumberToWeekDay((5 * (century % 4)) % 7 + 2);
-    };
-
-    const yearToAnchor = function (year) {
-        return dayNumberToWeekDay((new Date("" + year + "-04-04")).getDay());
-    };
 
 
-    const showError = function (input, errorLabel) {
+        /**
+         * Returns `undefined` if the element is valid, or an error message explaining why it is invalid otherwise.
+         *
+         * This method **must** be implemented by subclasses.
+         *
+         * @param value the value of the element to validate
+         */
+        validate(value) {
+            throw new Error("Implement this method.");
+        }
 
-    };
+        /**
+         * Runs when the user submits a valid input.
+         *
+         * This method **must** be implemented by subclasses.
+         */
+        onValidInput() {
+            throw new Error("Implement this method.");
+        }
+
+        /**
+         * Runs when a user submits an invalid input.
+         *
+         * This method **must** be implemented by subclasses.
+         */
+        onInvalidInput() {
+            throw new Error("Implement this method.");
+        }
+
+
+        /**
+         * Resets the element to its initial state, removing error messages and user input.
+         */
+        reset() {
+            this.element.dataset["entered"] = "false";
+            this.element.value = "";
+            this.element.setCustomValidity("");
+
+            this.errorLabel.classList.add("invisible");
+            this.errorLabel.innerText = "";
+        }
+
+        /**
+         * Focuses the input element.
+         */
+        focus() {
+            this.element.select();
+        }
+
+        /**
+         * Sets the title above the input.
+         *
+         * @param title the title to set
+         */
+        setTitle(title) {
+            this.titleLabel.innerText = title;
+        }
+    }
+
+    /**
+     * A wrapper around the good ol' `Date` class that provides a bunch of useful Doomsday-specific methods.
+     */
+    class DoomsdayDate {
+        /**
+         * Wraps a `DoomsdayDate` around the given `Date`.
+         *
+         * @param date the `Date` to be wrapped
+         */
+        constructor(date) {
+            this.date = date;
+        }
+
+
+        /**
+         * Returns the day of the week of the anchor of this `DoomsdayDate`'s century as a string.
+         */
+        getCenturyAnchorString() {
+            const yearNumber = this.date.getFullYear();
+            const centuryNumber = Math.floor(yearNumber / 100);
+            const centuryAnchorNumber = (5 * (centuryNumber % 4)) % 7 + 2;
+            return DoomsdayDate.dayNumberToString(centuryAnchorNumber);
+        };
+
+        /**
+         * Returns the day of the week of the anchor day of this `DoomsdayDate`'s year as a string.
+         */
+        getYearAnchorString() {
+            const anchorDate = new Date(this.date);
+            anchorDate.setMonth(3); // April
+            anchorDate.setDate(4); // 4th
+            return DoomsdayDate.dayNumberToString(anchorDate.getDay());
+        };
+
+        /**
+         * Returns the day of the week of this `DoomsdayDate` as a string.
+         */
+        getWeekdayString() {
+            return DoomsdayDate.dayNumberToString(this.date.getDay());
+        };
+
+
+        /**
+         * Returns the name of the day given its 0-based index, where 0 is `Sunday`.
+         *
+         * @param dayNumber the number of the day, as returned by `Date`'s `#getDay` function.
+         */
+        static dayNumberToString(dayNumber) {
+            switch (dayNumber % 7) {
+                case 0:
+                    return "Sunday";
+                case 1:
+                    return "Monday";
+                case 2:
+                    return "Tuesday";
+                case 3:
+                    return "Wednesday";
+                case 4:
+                    return "Thursday";
+                case 5:
+                    return "Friday";
+                case 6:
+                    return "Saturday";
+            }
+        };
+
+        /**
+         * Returns a random date in the range `0001-01-01` (inclusive) to `9999-12-31` (inclusive), wrapped inside a
+         * `DoomsdayDate` object.
+         */
+        static random() {
+            // TODO Give custom dates to this method
+            const minDate = new Date("0001-01-01").getTime() / 86400000;
+            const maxDate = new Date("9999-12-31").getTime() / 86400000;
+            return new DoomsdayDate(new Date(generateRandom(minDate, maxDate) * 86400000));
+        }
+    }
 
 
     doAfterLoad(() => {
-        const centuryInput = $("#century");
-        const centuryLabel = $("#century-label");
-        const yearInput = $("#year");
-        const yearLabel = $("#year-label");
-        const dayInput = $("#day");
-        const dayLabel = $("#day-label");
-
         let quizDate;
 
+        const centuryClass = new class extends ValidatableElement {
+            validate(value) {
+                return value === quizDate.getCenturyAnchorString() ? null : "";
+            }
 
-        const reloadQuiz = function () {
+            onValidInput() {
-            centuryInput.dataset["entered"] = "false";
+                console.log("valid");
-            centuryInput.value = "";
+                yearClass.focus();
-            yearInput.dataset["entered"] = "false";
+            }
-            yearInput.value = "";
-            dayInput.dataset["entered"] = "false";
-            dayInput.value = "";
 
-            quizDate = generateDate();
+            onInvalidInput() {
-            centuryLabel.innerText = Math.floor(quizDate.getFullYear() / 100) * 100;
+                // Do nothing
-            yearLabel.innerText = quizDate.getFullYear();
+            }
-            dayLabel.innerText = quizDate.toISOString().substr(0, 10);
+        }($("#century"), $("#century-label"), $("#century-error"));
+        const yearClass = new class extends ValidatableElement {
+            validate(value) {
+                return value === quizDate.getYearAnchorString() ? null : "";
+            }
 
-            centuryInput.select();
+            onValidInput() {
+                dayClass.focus();
+            }
+
+            onInvalidInput() {
+                // Do nothing
+            }
+        }($("#year"), $("#year-label"), $("#year-error"));
+        const dayClass = new class extends ValidatableElement {
+            validate(value) {
+                return value === quizDate.getWeekdayString() ? null : "";
+            }
+
+            onValidInput() {
+                reloadQuiz();
+            }
+
+            onInvalidInput() {
+                // Do nothing
+            }
+        }($("#day"), $("#day-label"), $("#day-error"));
+
+
+        function reloadQuiz() {
+            quizDate = DoomsdayDate.random();
+            centuryClass.reset();
+            yearClass.reset();
+            dayClass.reset();
+
+            centuryClass.setTitle("" + Math.floor(quizDate.date.getFullYear() / 100) * 100);
+            yearClass.setTitle("" + quizDate.date.getFullYear());
+            dayClass.setTitle("" + quizDate.date.toISOString().substr(0, 10));
+
+            centuryClass.focus();
+
+            // console.log(centuryToAnchor(quizDate));
+            // console.log(yearToAnchor(quizDate));
+            // console.log(dateToWeekDay(quizDate));
+        }
 
-            console.log(centuryToAnchor(Math.floor(quizDate.getFullYear() / 100)));
-            console.log(yearToAnchor(quizDate.getFullYear()));
-            console.log(dayNumberToWeekDay(quizDate.getDay()));
-        };
         reloadQuiz();
-
-
-        centuryInput.addEventListener("keydown", event => {
-            if (event.key === "Enter") {
-                centuryInput.dataset["entered"] = "true";
-                if (centuryInput.value === centuryToAnchor(Math.floor(quizDate.getFullYear() / 100))) {
-                    centuryInput.setCustomValidity("");
-                    yearInput.select();
-                } else {
-                    centuryInput.setCustomValidity("Wrong day");
-                    centuryInput.select();
-                }
-            }
-        });
-
-        yearInput.addEventListener("keydown", event => {
-            if (event.key === "Enter") {
-                yearInput.dataset["entered"] = "true";
-                if (yearInput.value === yearToAnchor(quizDate.getFullYear())) {
-                    yearInput.setCustomValidity("");
-                    dayInput.select();
-                } else {
-                    yearInput.setCustomValidity("Wrong day");
-                    yearInput.select();
-                }
-            }
-        });
-
-        dayInput.addEventListener("keydown", event => {
-            if (event.key === "Enter") {
-                dayInput.dataset["entered"] = "true";
-                if (dayInput.value === dayNumberToWeekDay(quizDate.getDay())) {
-                    reloadQuiz();
-                } else {
-                    dayInput.setCustomValidity("Wrong day");
-                    dayInput.select();
-                }
-            }
-        });
     });
 </script>
 </body>