await async

step2-01/src/types/index.ts

@@ -0,0 +1,52 @@
+// Basic Types
+let isDone: boolean = false;
+let decimal: number = 6;
+let color: string = 'blue';
+let sky: string = `the sky is ${color}`;
+
+// Function Types
+type FibFn = (n: number) => number;
+
+// Object Types
+type Obj = {
+  [key: string]: string;
+};
+
+// Object with Specified Keys
+type Specific1 = {
+  foo: string;
+  bar: number;
+  common: string;
+};
+
+type Specific2 = {
+  alice: string;
+  bob: number;
+  common: number;
+};
+
+// composition
+type typeofObj = {
+  foo: string;
+  bar: number;
+  obj: Specific1;
+};
+
+// union, intersection
+type Union = Specific1 | Specific2;
+type Intersection = Specific1 & Specific2;
+
+// casting
+let choose1 = <Specific1>{ common: '5' };
+
+// string literal union
+type CatStatus = 'alive' | 'dead' | 'both';
+
+// Classes
+class Animal {}
+
+// Illustration purposes only
+// In real apps, avoid inheritance if possible
+// noted exception: React.Component with react@<16.8.0
+class Cat extends Animal {}
+class Dog extends Animal {}