Solve p19 in js

README.rst

@@ -78,7 +78,7 @@ Olivia's Project Euler Solutions
 |            | Microsoft, Oracle, |br|    |        | |CodeQL| |br|     |
 |            | Semeru, Temurin, & Zulu    |        | |Java-lint|       |
 +------------+----------------------------+--------+-------------------+
-| JavaScript | Node 12+ |br|              | 25     | |JavaScript| |br| |
+| JavaScript | Node 12+ |br|              | 26     | |JavaScript| |br| |
 |            | Bun 1.0+ |br|              |        | |Js-Cov| |br|     |
 |            | Browser [#]_               |        | |CodeQL| |br|     |
 |            |                            |        | |ESLint|          |

docs/index.rst

@@ -112,7 +112,7 @@ Problems Solved
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`18` |            |            |            |            |            |:py-d:`0018`|:rs-d:`0018`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
-|:prob:`19` |            |            |            |            |            |:py-d:`0019`|:rs-d:`0019`|
+|:prob:`19` |            |            |            |            |:js-d:`0019`|:py-d:`0019`|:rs-d:`0019`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+
 |:prob:`20` |:c-d:`0020` |:cp-d:`0020`|:cs-d:`0020`|:ja-d:`0020`|:js-d:`0020`|:py-d:`0020`|:rs-d:`0020`|
 +-----------+------------+------------+------------+------------+------------+------------+------------+

docs/src/javascript/p0019.rst

@@ -0,0 +1,12 @@
+JavaScript Implementation of Problem 19
+=======================================
+
+View source code :source:`javascript/src/p0019.js`
+
+.. js:autofunction:: p0019
+
+.. literalinclude:: ../../../javascript/src/p0019.js
+   :language: javascript
+   :linenos:
+
+.. tags:: calendar, combinatorics

javascript/src/p0019.js

@@ -0,0 +1,36 @@
+/**
+ * Project Euler Problem 19
+ *
+ * This one ended up being very easy thanks to the Date object
+ *
+ * Problem:
+ *
+ * You are given the following information, but you may prefer to do some research
+ * for yourself.
+ *
+ * 1 Jan 1900 was a Monday.
+ * Thirty days has September,
+ * April, June and November.
+ * All the rest have thirty-one,
+ * Saving February alone,
+ * Which has twenty-eight, rain or shine.
+ * And on leap years, twenty-nine.
+ * A leap year occurs on any year evenly divisible by 4, but not on a century
+ * unless it is divisible by 400.
+ *
+ * How many Sundays fell on the first of the month during the twentieth century
+ * (1 Jan 1901 to 31 Dec 2000)?
+ *
+ * @return {number}
+ */
+exports.p0019 = function() {
+    let answer = 0;
+    for (let x = 1901; x < 2001; x += 1) {
+        for (let y = 1; y < 13; y += 1) {
+            if (new Date(x, y, 1).getDay() == 0) {
+                answer += 1;
+            }
+        }
+    }
+    return answer;
+};