Add ES9 features

Author: sudheerj

README.md

@@ -1386,10 +1386,10 @@ Each proposal for an ECMAScript feature goes through the following maturity stag
    1. You can pass object to a function
 
        ```js
-        function myfunc({ a, ...x }) {
+        function myfunc1({ a, ...x }) {
             console.log(a, x); // 1, { b: 2, c: 3, d:4 }
         }
-        myfunc({
+        myfunc1({
           a: 1,
           b: 2,
           c: 3,

es2018/1.async-iterators.js

@@ -0,0 +1,8 @@
+const arr = ['a', 'b', 'c', 'd'];
+const syncIterator = arr[Symbol.iterator]();
+
+console.log(syncIterator.next());    //{value: a, done: false}
+console.log(syncIterator.next());    //{value: b, done: false}
+console.log(syncIterator.next());    //{value: c, done: false}
+console.log(syncIterator.next());    //{value: d, done: false}
+console.log(syncIterator.next());    //{value: undefined, done: true}

es2018/2.object-rest-spread-operators.js

@@ -0,0 +1,25 @@
+// Rest parameters
+
+function myfunc(p1, p2, ...p3) {
+    console.log(p1, p2, p3); // 1, 2, [3, 4, 5, 6]
+}
+myfunc(1, 2, 3, 4, 5, 6);
+
+// spread operator
+const myArray = [10, 5, 25, -100, 200, -200];
+console.log( Math.max(...myArray) ); // 200
+
+// Rest parameters for objects
+function myfunc1({ a, ...x }) {
+    console.log(a, x); // 1, { b: 2, c: 3, d:4 }
+}
+myfunc1({
+    a: 1,
+    b: 2,
+    c: 3,
+    d: 4
+});
+
+// spread operator for objects
+const myObject = { a: 1, b: 2, c: 3, d:4 };
+const myNewObject = { ...myObject, e: 5 }; // { a: 1, b: 2, c: 3, d: 4, e: 5 }

es2018/3.promise-finally.js

@@ -0,0 +1,8 @@
+let isLoading = true;
+fetch('http://somesite.com/users')
+    .then(data => data.json())
+    .catch(err => console.error(err))
+    .finally(() => {
+        isLoading = false;
+        console.log('Finished loading!!');
+    })