Added advanced types

chapter02/src/types_advanced.js

@@ -15,5 +15,109 @@ function addTwo(x: numberOrString, y: numberOrString) {
     return x + y;
 }
 
-const fs: any = require("fs");
-fs.readFile("/somefilename.ext", processData);
+class Person {
+    // class fields need Flow annotations
+    first: string;
+    last: string;
+
+    constructor(first, last) {
+        this.first = first;
+        this.last = last;
+    }
+
+    initials(): string {
+        return `${this.first[0]}${this.last[0]}`;
+    }
+
+    fullName(): string {
+        return `${this.first} ${this.last}`;
+    }
+
+    get lastFirst(): string {
+        return `${this.last}, ${this.first}`;
+    }
+
+    set lastFirst(lf: string) {
+        // very unsafe; no checks!
+        const parts = lf.split(",");
+        this.last = parts[0];
+        this.first = parts[1];
+    }
+}
+
+let pp = new Person("Jan", "Jansen"); // OK
+let qq = new Person(1, 2); // error: wrong types for the constructor
+let rr: Person; // OK, "Person" type is understood and can be used
+
+const identity = <T>(x: T): T => x;
+
+function identity2<T>(x: T): T {
+    return x;
+}
+
+function identity3<T>(x: T): T {
+    return 229; // wrong; this is always a number, not generic
+}
+
+function makeObject<T1, T2>(x: T1, y: T2) {
+    return { first: x, second: y };
+}
+
+type pair<T> = [T, T];
+
+type pairOfNumbers = pair<number>;
+type pairOfStrings = pair<string>;
+
+let pn: pairOfNumbers = [22, 9];
+let ps: pairOfStrings = ["F", "K"];
+
+type simpleFlag = number | boolean;
+type complexObject = {
+    id: string,
+    name: string,
+    indicator: simpleFlag,
+    listOfValues: Array<number>
+};
+
+let myFlag: simpleFlag;
+let something: complexObject = {
+    id: "B2209",
+    name: "Anna Malli",
+    indicator: 1,
+    listOfValues: [12, 4, 56]
+};
+
+class Animal {
+    name: string;
+    species: string;
+    age: number;
+}
+
+class Pet {
+    name: string;
+    species: string;
+    age: number;
+}
+
+let tom: Animal;
+tom = new Pet(); // error: Pet and Animal are distinct types
+
+interface AnimalInt {
+    name: string;
+    species: string;
+    age: number;
+}
+
+class Animal2 implements AnimalInt {
+    name: string;
+    species: string;
+    age: number;
+}
+class Pet2 implements AnimalInt {
+    name: string;
+    species: string;
+    age: number;
+}
+
+let tom2: AnimalInt;
+tom2 = new Pet2();