Add iterable examples

Author: tshemsedinov

JavaScript/f-iterator.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const range = {
+  start: 1,
+  end: 10,
+  [Symbol.iterator]() {
+    let value = this.start;
+    return {
+      next: () => ({
+        value,
+        done: value++ === this.end + 1
+      })
+    };
+  }
+};
+
+console.dir({
+  range,
+  names: Object.getOwnPropertyNames(range),
+  symbols: Object.getOwnPropertySymbols(range),
+});
+
+for (const number of range) {
+  console.log(number);
+}
+
+const sum = (prev, cur) => prev + cur;
+const sumIterable = (...iterable) => iterable.reduce(sum);
+
+const sumRange = sumIterable(...range);
+console.log('sumRange:', sumRange);

JavaScript/g-reverse.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const arr = [2, 5, -1, 7, 0];
+
+arr[Symbol.iterator] = function() {
+  let index = this.length;
+  return {
+    next: () => ({
+      done: index-- === 0,
+      value: this[index]
+    })
+  };
+};
+
+for (const number of arr) {
+  console.log(number);
+}