Unique characters in each string: Difference between revisions

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       "3ycxdb1fgxa2yz"
     ]</lang>
+{{Out}}
+<pre>123abc</pre>
+=={{header|JavaScript}}==
+<lang javascript>(() => {
+    "use strict";
+    // onceInEach :: [String] -> String
+    const onceInEach = ws =>
+        // Characters which occur exactly once
+        // in each word in the list.
+< ws.length ? (() => {
+            const
+                wordCount = ws.length,
+                charFreqs = charCounts(ws.join("")),
+                shared = ws.slice(1).reduce(
+                    (a, x) => intersect(a)(new Set([...x])),
+                    new Set([...ws[0]])
+                );
+            return sort(
+                [...shared].filter(
+                    c => wordCount === charFreqs[c]
+                )
+            ).join("");
+        })() : "";
+    // ---------------------- TEST -----------------------
+    const main = () =>
+        onceInEach([
+            "1a3c52debeffd",
+            "2b6178c97a938stf",
+            "3ycxdb1fgxa2yz"
+        ]);
+    // --------------------- GENERIC ---------------------
+    // charCounts :: String -> Dict Char Int
+    const charCounts = cs =>
+        // Dictionary of chars, with the
+        // frequency of each in cs.
+        [...cs].reduce(
+            (a, c) => Object.assign(
+                a, {
+                    [c]: 1 + (a[c] || 0)
+                }
+            ), {}
+        );
+    // intersect :: Set -> Set -> Set
+    const intersect = a =>
+        // The intersection of two sets.
+        b => new Set([...a].filter(i => b.has(i)));
+    // sort :: Ord a => [a] -> [a]
+    const sort = xs =>
+        // An A-Z sorted copy of xs.
+        [...xs].slice().sort(
+            (a, b) => a < b ? -1 : (a > b ? 1 : 0)
+        );
+    // MAIN ---
+    return main();
+})();</lang>
 {{Out}}
 <pre>123abc</pre>