Set operations example

tshemsedinov · tshemsedinov · commit ee0e2f4bcbd7 · 2017-11-18T12:28:17.000+02:00
diff --git a/JavaScript/2-distinct.js b/JavaScript/2-distinct.js
@@ -1,6 +1,6 @@
 'use strict';
 
-function distinct(dataset) {
+const distinct = (dataset) => {
   const keys = new Set();
   return dataset.filter(record => {
     const cols = Object.keys(record).sort();
@@ -9,9 +9,11 @@ function distinct(dataset) {
     keys.add(key);
     return !has;
   });
-}
+};
 
-let flights = [
+// Usage
+
+const flights = [
   { from: 'Kiev', to: 'Rome' },
   { from: 'Kiev', to: 'Warsaw' },
   { from: 'Dublin', to: 'Riga' },
@@ -22,6 +24,6 @@ let flights = [
 
 console.dir({ flights });
 
-flights = distinct(flights);
+const directions = distinct(flights);
 
-console.dir({ flights });
+console.dir({ directions });
diff --git a/JavaScript/3-operations.js b/JavaScript/3-operations.js
@@ -0,0 +1,27 @@
+'use strict';
+
+const union = (s1, s2) => new Set([...s1, ...s2]);
+
+const intersection = (s1, s2) => new Set(
+  [...s1].filter(v => s2.has(v))
+);
+
+const difference = (s1, s2) => new Set(
+  [...s1].filter(v => !s2.has(v))
+);
+
+const complement = (s1, s2) => difference(s2, s1);
+
+// Usage
+
+const cities1 = new Set(['Beijing', 'Kiev']);
+const cities2 = new Set(['Kiev', 'London', 'Baghdad']);
+
+const operations = [union, intersection, difference, complement];
+
+const results = operations.map(operation => ({
+  [operation.name]: operation(cities1, cities2)
+}));
+
+console.dir({ cities1, cities2 });
+console.dir(results);
