Solve p3 in js; fix linting

README.rst

@@ -67,7 +67,7 @@ Olivia's Project Euler Solutions
 |            |                          |        | |CodeQL| |br|     |
 |            |                          |        | |C#-lint|         |
 +------------+--------------------------+--------+-------------------+
-| JavaScript | Node 12+ |br|            | 17     | |JavaScript| |br| |
+| JavaScript | Node 12+ |br|            | 18     | |JavaScript| |br| |
 |            | Bun 1.0+ |br|            |        | |Js-Cov| |br|     |
 |            | Firefox [2]_ |br|        |        | |CodeQL| |br|     |
 |            | Chrome [2]_              |        | |ESLint|          |

docs/index.rst

@@ -72,7 +72,7 @@ Problems Solved
 +-----------+------------+------------+------------+------------+------------+------------+
 |:prob:`2`  |:c-d:`0002` |:cp-d:`0002`|:cs-d:`0002`|:js-d:`0002`|:py-d:`0002`|:rs-d:`0002`|
 +-----------+------------+------------+------------+------------+------------+------------+
-|:prob:`3`  |:c-d:`0003` |            |            |            |:py-d:`0003`|:rs-d:`0003`|
+|:prob:`3`  |:c-d:`0003` |            |            |:js-d:`0003`|:py-d:`0003`|:rs-d:`0003`|
 +-----------+------------+------------+------------+------------+------------+------------+
 |:prob:`4`  |:c-d:`0004` |:cp-d:`0004`|:cs-d:`0004`|:js-d:`0004`|:py-d:`0004`|:rs-d:`0004`|
 +-----------+------------+------------+------------+------------+------------+------------+

docs/javascript/p0003.rst

@@ -0,0 +1,18 @@
+JavaScript Implementation of Problem 3
+======================================
+
+View source code :source:`javascript/src/p0003.js`
+
+Includes
+--------
+
+- `primes <./primes.html>`_
+
+Problem Solution
+----------------
+
+.. js:autofunction:: p0003
+
+.. literalinclude:: ../../javascript/src/p0003.js
+   :language: javascript
+   :linenos:

docs/javascript/p0007.rst

@@ -3,6 +3,14 @@ JavaScript Implementation of Problem 7
 
 View source code :source:`javascript/src/p0007.js`
 
+Includes
+--------
+
+- `primes <./primes.html>`_
+
+Problem Solution
+----------------
+
 .. js:autofunction:: p0007
 
 .. literalinclude:: ../../javascript/src/p0007.js

docs/javascript/primes.rst

@@ -3,8 +3,12 @@ primes.js
 
 View source code :source:`javascript/src/lib/primes.js`
 
+.. js:autofunction:: primes.primes
+
 .. js:autofunction:: primes.modifiedEratosthenes
 
+.. js:autofunction:: primes.primeFactors
+
 .. literalinclude:: ../../javascript/src/lib/primes.js
    :language: javascript
    :linenos:

javascript/euler.test.js

@@ -21,6 +21,7 @@ describe('Mathematics', ()=>{
 const answers = {
     1: [require('./src/p0001.js'), false],
     2: [require('./src/p0002.js'), false],
+    3: [require('./src/p0003.js'), false],
     4: [require('./src/p0004.js'), false],
     6: [require('./src/p0006.js'), false],
     7: [require('./src/p0007.js'), false],

javascript/src/lib/primes.js

@@ -1,3 +1,48 @@
+const cache = [2, 3, 5, 7];
+let lastCached = 7;
+
+/**
+ * Iterates over the prime numbers up to an (optional) limit, with caching.
+ *
+ * This iterator leverages the :js:func:`primes.modifiedEratosthenes` iterator, but adds
+ * additional features. The biggest is a ``stop`` argument, which will prevent it
+ * from yielding any numbers larger than that. The next is caching of any yielded
+ * prime numbers.
+ * @param {number | null} stop
+ * @yield {number}
+ */
+function* primes(stop = null) {
+    if (stop === null) {
+        for (p of cache) {
+            yield p;
+        }
+    } else {
+        for (p of cache) {
+            if (p < stop) {
+                yield p;
+            } else {
+                break;
+            }
+        }
+    }
+    if (stop !== null && lastCached > stop) {
+        return;
+    }
+    for (p of modifiedEratosthenes()) {
+        if (p <= lastCached) {
+            continue;
+        }
+        if (stop !== null && p > stop) {
+            break;
+        }
+        cache.push(p);
+        lastCached = p;
+        yield p;
+    }
+}
+exports.primes = primes;
+
+
 /**
  * Iterates over prime numbers using the Sieve of Eratosthenes.
  *
@@ -6,44 +51,80 @@
  * the principle of the sieve.
  *
  * .. image:: https://upload.wikimedia.org/wikipedia/commons/9/94/Animation_Sieve_of_Eratosth.gif
- *      :alt: Any animated example of the Sieve of Eratosthenes"""
- * @param {number} n
- * @return {number}
+ *      :alt: Any animated example of the Sieve of Eratosthenes
+ * @yield {number}
  */
-exports.modifiedEratosthenes = function * modifiedEratosthenes(n) {
+function* modifiedEratosthenes() {
     yield 2;
     yield 3;
     yield 5;
     yield 7;
     const sieve = new Map();
-    const recurse = modifiedEratosthenes();
+    const recurse = primes();
     recurse.next();
     let prime = recurse.next().value;
     if (prime !== 3) {
         throw new Error();
     }
-    let prime_squared = prime * prime;
+    let primeSquared = prime * prime;
     let step = 2;
     for (let candidate = 9; ; candidate += 2) {
-        if (sieve.has(candidate)) {  // if c is a multiple of some base prime, or
+        if (sieve.has(candidate)) { // if c is a multiple of some base prime, or
             step = sieve.get(candidate);
             sieve.delete(candidate);
-        }
-        else if (candidate < prime_squared) {  // prime, or
+        } else if (candidate < primeSquared) { // prime, or
             yield candidate;
             continue;
-        }
-        else {  // the next base prime's square
-            // if candidate != prime_squared:
+        } else { // the next base prime's square
+            // if candidate != primeSquared:
             //     raise ValueError()
             step = prime * 2;
             prime = recurse.next().value;
-            prime_squared = prime * prime;
+            primeSquared = prime * prime;
         }
-        let tc = candidate
+        let tc = candidate;
         do {
-            tc += step;  // the next multiple
-        } while (sieve.has(tc))  // make sure to not overwrite another sieve entry
+            tc += step; // the next multiple
+        } while (sieve.has(tc)); // make sure to not overwrite another sieve entry
         sieve.set(tc, step);
     }
-};
+}
+exports.modifiedEratosthenes = modifiedEratosthenes;
+
+
+/**
+ * Iterates over the prime factors of a number.
+ *
+ * @param {number} num
+ * @yield {number}
+ */
+function* primeFactors(num) {
+    if (num < 0) {
+        yield -1;
+        num = -num;
+    }
+    if (num === 0) {
+        yield 0;
+    } else {
+        let root = Math.ceil(Math.sqrt(num));
+        for (factor of primes()) {
+            let modulo = num % factor;
+            if (modulo == 0) {
+                while (modulo == 0) { // double-check to call sqrt once
+                    yield factor;
+                    num /= factor;
+                    modulo = num % factor;
+                }
+                root = Math.ceil(Math.sqrt(num));
+            }
+            if (num <= 1) {
+                break;
+            }
+            if (factor > root) {
+                yield num;
+                break;
+            }
+        }
+    }
+}
+exports.primeFactors = primeFactors;

javascript/src/p0003.js

@@ -0,0 +1,19 @@
+/**
+ * Project Euler Problem 3
+ *
+ * Finally ported prime factor generator to js
+ *
+ * Problem:
+ *
+ * The prime factors of 13195 are 5, 7, 13 and 29.
+ *
+ * What is the largest prime factor of the number 600851475143 ?
+ *
+ * @return {number}
+ */
+exports.p0003 = function() {
+    return Math.max(...primes.primeFactors(600851475143));
+};
+
+const primes = require('./lib/primes.js');
+

javascript/src/p0007.js

@@ -13,14 +13,13 @@
  * @return {number}
  */
 exports.p0007 = function() {
-    let pgen = primes.modifiedEratosthenes();
+    const pgen = primes.modifiedEratosthenes();
     for (let idx = 1; ; idx++) {
-        let num = pgen.next().value;
+        const num = pgen.next().value;
         if (idx === 10001) {
             return num;
         }
     }
-    return -1;
 };
 
 const primes = require('./lib/primes.js');