Initial data commit

Task/Convert-decimal-number-to-rational/JavaScript/convert-decimal-number-to-rational.js

@@ -0,0 +1,49 @@
+(() => {
+    'use strict';
+
+    const main = () =>
+        showJSON(
+            map( // Using a tolerance epsilon of 1/10000
+                n => showRatio(approxRatio(0.0001)(n)),
+                [0.9054054, 0.518518, 0.75]
+            )
+        );
+
+    // Epsilon -> Real -> Ratio
+
+    // approxRatio :: Real -> Real -> Ratio
+    const approxRatio = eps => n => {
+        const
+            gcde = (e, x, y) => {
+                const _gcd = (a, b) => (b < e ? a : _gcd(b, a % b));
+                return _gcd(Math.abs(x), Math.abs(y));
+            },
+            c = gcde(Boolean(eps) ? eps : (1 / 10000), 1, n);
+        return Ratio(
+            Math.floor(n / c), // numerator
+            Math.floor(1 / c) // denominator
+        );
+    };
+
+    // GENERIC FUNCTIONS ----------------------------------
+
+    // Ratio :: Int -> Int -> Ratio
+    const Ratio = (n, d) => ({
+        type: 'Ratio',
+        'n': n, // numerator
+        'd': d // denominator
+    });
+
+    // map :: (a -> b) -> [a] -> [b]
+    const map = (f, xs) => xs.map(f);
+
+    // showJSON :: a -> String
+    const showJSON = x => JSON.stringify(x, null, 2);
+
+    // showRatio :: Ratio -> String
+    const showRatio = nd =>
+        nd.n.toString() + '/' + nd.d.toString();
+
+    // MAIN ---
+    return main();
+})();