Created basic files; still incomplete

chapter01/.flowconfig

@@ -0,0 +1,11 @@
+[ignore]
+
+[include]
+
+[libs]
+
+[lints]
+
+[options]
+
+[strict]

chapter02/.flowconfig

@@ -0,0 +1,11 @@
+[ignore]
+
+[include]
+
+[libs]
+
+[lints]
+
+[options]
+
+[strict]

chapter02/package.json

@@ -26,7 +26,7 @@
             "node": true
         },
         "extends": ["eslint:recommended", "plugin:flowtype/recommended"],
-        "plugins": ["flowtype"],
+        "plugins": ["babel", "flowtype"],
         "rules": {
             "no-console": "off"
         }

chapter02/src/extdate.js

@@ -1,3 +1,5 @@
+// @flow
+
 class ExtDate extends Date {
     fullDate() {
         const months = [

chapter02/src/persons.js

@@ -24,7 +24,7 @@ class Person {
     }
 }
 
-pp = new Person("Erika", "Mustermann");
+let pp = new Person("Erika", "Mustermann");
 console.log(pp); // Person {first: "Erika", last: "Mustermann"}
 console.log(pp.initials()); // "EM"
 console.log(pp.fullName()); // "Erika Mustermann"
@@ -44,7 +44,7 @@ class Developer extends Person {
     }
 }
 
-window.dd = new Developer("John", "Doe", "JS");
+let dd = new Developer("John", "Doe", "JS");
 console.log(dd); // Developer {first: "John", last: "Doe", language: "JS"}
 console.log(dd.initials()); // "JD"
 console.log(dd.fullName()); // "John Doe, JS dev"
@@ -63,22 +63,19 @@ const countKeysMixin = base =>
         }
     };
 
-    class PersonWithTwoMixins extends toJsonMixin(countKeysMixin(Person)) {
+class PersonWithTwoMixins extends toJsonMixin(countKeysMixin(Person)) {
     toJson() {
         // redefine the method, just for the sake of it
         return "NEW TOJSON " + super.toJson();
     }
-    }
+}
 
+let p2m = new PersonWithTwoMixins("Jane", "Roe");
+console.log(p2m);
+console.log(p2m.toJson()); // NEW TOJSON {"first":"Jane","last":"Roe"}
+console.log(p2m.countKeys()); // 2
 
-    p2m = new PersonWithTwoMixins("Jane", "Roe");
-    console.log(p2m);
-    console.log(p2m.toJson());    // NEW TOJSON {"first":"Jane","last":"Roe"}
-    console.log(p2m.countKeys()); // 2
-
-
-
-    class ExtDate extends Date {
+class ExtDate extends Date {
     fullDate() {
         const months = [
             "JAN",
@@ -104,7 +101,6 @@ const countKeysMixin = base =>
         );
     }
 
-    
     static getMonthName(m) {
         const months = [
             "JAN",
@@ -125,6 +121,6 @@ const countKeysMixin = base =>
             this.getFullYear()
         );
     }
-    }
+}
 
-    console.log(new ExtDate().fullDate()); // "MAY 01 2018"
+console.log(new ExtDate().fullDate()); // "MAY 01 2018"

chapter02/src/types_advanced.js

@@ -0,0 +1,19 @@
+/* @flow */
+/* eslint-disable no-unused-vars */
+
+let flag: number | boolean;
+flag = true; // OK
+flag = 1; // also OK
+flag = "1"; // error: wrong type
+
+let traffic: "red" | "amber" | "green"; // traffic is implicitly string
+traffic = "yellow"; // error: not allowed
+
+type numberOrString = number | string;
+
+function addTwo(x: numberOrString, y: numberOrString) {
+    return x + y;
+}
+
+const fs: any = require("fs");
+fs.readFile("/somefilename.ext", processData);

chapter02/src/types_basic.js

@@ -0,0 +1,33 @@
+/* @flow */
+/* eslint-disable no-unused-vars */
+
+let someFlag: boolean;
+let greatTotal: number;
+let firstName: string;
+
+function toString(x: number): string {
+    return String(x);
+}
+
+function addTwo(x: number | string, y: number | string) {
+    return x + y;
+}
+
+function showValue(z: mixed): void {
+    // not returning anything
+    console.log("Showing... ", z);
+}
+
+let numbersList: Array<number>;
+numbersList = [22, 9, 60]; // OK
+numbersList[1] = "SEP"; // error; cannot assign a string to a number
+
+let anotherList: number[];
+
+let sealedObject: { name: string, age?: number };
+sealedObject.name = "Ivan Horvat"; // OK
+sealedObject.id = 229; // error: key isn't defined in the data type
+sealedObject = { age: 57 }; // error: mandatory field is missing
+
+let unsealedObject = {};
+unsealedObject.id = 229; // OK