Update tasks

Author: tshemsedinov

JavaScript/Tasks/2-promise.js

@@ -1,19 +1,17 @@
 'use strict';
 
-// Task: change `iterate` contract from chainable callbacks
-// to Promise (chainable or you can call it with await syntax)
+// Task: rewrite `total` from callbacks contract to promises
 
-const iterate = (items) => {
-  let index = 0;
-  const chain = {
-    next: (callback) => {
-      if (index < items.length) {
-        callback(items[index++]);
-      }
-      return chain;
+const total = (items, callback) => {
+  let result = 0;
+  for (const item of items) {
+    if (item.price < 0) {
+      callback(new Error('Negative price is not allowed'));
+      return;
     }
-  };
-  return chain;
+    result += item.price;
+  }
+  callback(null, result);
 };
 
 const electronics = [
@@ -22,11 +20,7 @@ const electronics = [
   { name: 'HDMI cable', price: 10 },
 ];
 
-// Use await syntax to get items
-iterate(electronics).next((item) => {
-  console.log(item);
-}).next((item) => {
-  console.log(item);
-}).next((item) => {
-  console.log(item);
+total(electronics, (error, money) => {
+  if (error) console.error({ error });
+  else console.log({ money });
 });

JavaScript/Tasks/4-chain.js renamed to JavaScript/Tasks/3-chain.js

@@ -0,0 +1,32 @@
+'use strict';
+
+// Task: change `iterate` contract from chainable callbacks
+// to Promise (chainable or you can call it with await syntax)
+
+const iterate = (items) => {
+  let index = 0;
+  const chain = {
+    next: (callback) => {
+      if (index < items.length) {
+        callback(items[index++]);
+      }
+      return chain;
+    }
+  };
+  return chain;
+};
+
+const electronics = [
+  { name: 'Laptop', price: 1500 },
+  { name: 'Keyboard', price: 100 },
+  { name: 'HDMI cable', price: 10 },
+];
+
+// Use await syntax to get items
+iterate(electronics).next((item) => {
+  console.log(item);
+}).next((item) => {
+  console.log(item);
+}).next((item) => {
+  console.log(item);
+});

JavaScript/Tasks/4-iterate.js

@@ -3,6 +3,7 @@
 // Task: support rejection with an error, if no more items in
 // `items` array are available to return with `.next()`
 // Change throwing error to returning rejected Promise.
+// Catch error with `.catch` or `try/catch` to handle it.
 
 const iterate = (items) => {
   let index = 0;