Data commit

Task/Hash-join/JavaScript/hash-join.js

@@ -0,0 +1,55 @@
+(() => {
+    'use strict';
+
+    // hashJoin :: [Dict] -> [Dict] -> String -> [Dict]
+    let hashJoin = (tblA, tblB, strJoin) => {
+
+        let [jA, jB] = strJoin.split('='),
+            M = tblB.reduce((a, x) => {
+                let id = x[jB];
+                return (
+                    a[id] ? a[id].push(x) : a[id] = [x],
+                    a
+                );
+            }, {});
+
+        return tblA.reduce((a, x) => {
+            let match = M[x[jA]];
+            return match ? (
+                a.concat(match.map(row => dictConcat(x, row)))
+            ) : a;
+        }, []);
+    },
+
+    // dictConcat :: Dict -> Dict -> Dict
+    dictConcat = (dctA, dctB) => {
+        let ok = Object.keys;
+        return ok(dctB).reduce(
+            (a, k) => (a['B_' + k] = dctB[k]) && a,
+            ok(dctA).reduce(
+                (a, k) => (a['A_' + k] = dctA[k]) && a, {}
+            )
+        );
+    };
+
+
+    // TEST
+    let lstA = [
+        { age: 27, name: 'Jonah' },
+        { age: 18, name: 'Alan' },
+        { age: 28, name: 'Glory' },
+        { age: 18, name: 'Popeye' },
+        { age: 28, name: 'Alan' }
+    ],
+    lstB = [
+        { character: 'Jonah', nemesis: 'Whales' },
+        { character: 'Jonah', nemesis: 'Spiders' },
+        { character: 'Alan', nemesis: 'Ghosts' },
+        { character:'Alan', nemesis: 'Zombies' },
+        { character: 'Glory', nemesis: 'Buffy' },
+        { character: 'Bob', nemesis: 'foo' }
+    ];
+
+    return hashJoin(lstA, lstB, 'name=character');
+
+})();