Add tasks

Author: tshemsedinov

JavaScript/Tasks/1-thenable.js

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+'use strict';
+
+// Task: change `iterate` contract from callbacks to Thenable
+
+const iterate = (items, callback) => {
+  for (const item of items) {
+    callback(item);
+  }
+};
+
+const electronics = [
+  { name: 'Laptop', price: 1500 },
+  { name: 'Keyboard', price: 100 },
+  { name: 'HDMI cable', price: 10 },
+];
+
+// Use await syntax to get items
+iterate(electronics, (item) => {
+  console.log(item);
+});

JavaScript/Tasks/2-reject.js

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+'use strict';
+
+// Task: support rejection with an error after last item
+
+const iterate = (items) => {
+  let index = 0;
+  return {
+    then(fulfill, /*reject*/) {
+      // Call both: fulfill and reject
+      if (index < items.length) {
+        fulfill(items[index++]);
+      }
+    }
+  };
+};
+
+const electronics = [
+  { name: 'Laptop', price: 1500 },
+  { name: 'Keyboard', price: 100 },
+  { name: 'HDMI cable', price: 10 },
+];
+
+(async () => {
+  const items = iterate(electronics);
+  const item1 = await items;
+  console.log(item1);
+  const item2 = await items;
+  console.log(item2);
+  const item3 = await items;
+  console.log(item3);
+  const item4 = await items;
+  console.log(item4);
+})();

JavaScript/Tasks/3-class.js

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+'use strict';
+
+// Task: rewrite to `class Iterator` implementing
+// Thenable contract with private fields.
+
+const iterate = (items) => {
+  let index = 0;
+  return {
+    then(fulfill, /*reject*/) {
+      if (index < items.length) {
+        fulfill(items[index++]);
+      }
+    }
+  };
+};
+
+const electronics = [
+  { name: 'Laptop', price: 1500 },
+  { name: 'Keyboard', price: 100 },
+  { name: 'HDMI cable', price: 10 },
+];
+
+(async () => {
+  const items = iterate(electronics);
+  // Use `new Iterator(electronics)`
+  const item1 = await items;
+  console.log(item1);
+  const item2 = await items;
+  console.log(item2);
+  const item3 = await items;
+  console.log(item3);
+  const item4 = await items;
+  console.log(item4);
+})();