promise belanja

beli.js

@@ -1,15 +1,18 @@
-function beli(uang, obj, cb){
-  console.log(`Saya pergi membeli ${obj.item}`)
-  setTimeout(function(){
-    let kembalian = uang - obj.harga
-    if (kembalian > 0) {
-      console.log(`Saya sudah membeli ${obj.item} uang kembaliannya ${kembalian}`);
-      cb(kembalian)
-    }else{
-      console.log(`uang gk cukup nih buat beli ${obj.item} kembaliannya cuma ${kembalian}`);
-      cb(0)
-    }
-  }, obj.waktu);
+class Belanja {
+  static beli(uang, obj) {
+    return new Promise((resolve, reject)=>{
+      console.log(`Saya pergi membeli ${obj.item}`)
+      setTimeout(()=>{
+        let kembalian = uang - obj.harga
+        if(kembalian > obj.harga) {
+          console.log(`Saya sudah membeli ${obj.item} uang kembaliannya ${kembalian}`)
+          resolve(kembalian)
+        } else {
+          reject(`uang gak cukup nih buat beli ${obj.item} kembaliannya cuma ${kembalian}`)
+        }
+      }, obj.waktu)
+    })
+  }
 }
 
-module.exports = beli;
+module.exports = Belanja;

index.js

@@ -0,0 +1,14 @@
+const Belanja = require('./beli.js')
+
+let indomie =  {item: 'indomie', harga: 1500, time: 500}
+let sarden =  {item: 'sarden', harga: 7000, waktu: 500}
+let gula = {item : 'gula', harga: 4000, waktu: 500}
+let garam = {item : 'garam', harga: 3000, waktu: 500}
+let royco = {item : 'royco', harga: 2000, waktu: 500}
+
+Belanja.beli(10000, indomie)
+  .then(kembalian => {Belanja.beli(kembalian, sarden)
+    .then(kembalian => {Belanja.beli(kembalian, gula)
+      .then(kembalian => {Belanja.beli(kembalian, garam)
+        .then(kembalian => {Belanja.beli(kembalian, royco)})})})
+        .catch(err => {console.log(err)})})