Changed type definition for once()

chapter02/src/functional_code.js

@@ -1,9 +1,9 @@
 /* @flow */
 
 type genericFunction = (...args: Array<mixed>) => mixed;
-type higherOrderFunction = genericFunction => genericFunction;
+type voidFunction = (...args: Array<mixed>) => void;
 
-const once: higherOrderFunction = (fn: genericFunction) => {
+const once = (fn: genericFunction): voidFunction => {
     let done = false;
     return (...args) => {
         if (!done) {

chapter02/src/spread_and_rest.js

@@ -0,0 +1,24 @@
+/* @flow */
+/* eslint-disable no-unused-vars */
+
+let values = [22, 9, 60, 12, 4, 56];
+const maxOfValues = Math.max(...values); // 60
+const minOfValues = Math.min(...values); // 4
+
+let arr1 = [1, 1, 2, 3];
+let arr2 = [13, 21, 34];
+let copyOfArr1 = [...arr1];
+let fibArray = [0, ...arr1, 5, 8, ...arr2]; // the first 10 Fibonacci numbers
+
+let person = { name: "Juan", age: 24 };
+let copyOfPerson = { ...person };
+let expandedPerson = { ...person, sister: "María" };
+
+const average = (...nums: Array<number>): number => {
+    let sum = 0;
+    for (let i = 0; i < nums.length; i++) {
+        sum += nums[i];
+    }
+    return sum / nums.length;
+};
+console.log(average(22, 9, 60, 12, 4, 56)); // 27.166667