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added some exercise bits to step 2.1
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@@ -1,8 +1,87 @@
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# Step 2.1
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Typescript
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## Introduction to Typescript
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- ES6 modules review
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- a look at types
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- defining interfaces
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-
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In this exercise, we'll cover enough of the Typescript concepts to be productive with the React & Redux frameworks.
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Topics in this Exercise will include:
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- ES modules
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- Basic Types
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- Interfaces & Classes
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- Basic Generics
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- Spread and Destructuring
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- Async / Await
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## Exercise
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Please complete all exercises inside the `exercise/src` folder unless otherwise specified in the exercises below. First, open up [Step2-01 exercise page](http://localhost:8080/step2-01/exercise/) to see the results while you're implementing things.
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### Modules
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1. Open up file called `index.ts` in VS Code
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2. Create another module file called `fibonacci.ts`
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3. Inside the file from (step 2), write a function called `fib(n)` that takes in a number and returns a the n-th Fibonacci number - be sure the specify the type of n
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4. Export `fib(n)` as a **named export**
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5. Export another const variable as a **default export**
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6. Import both the modules created in steps (4) and (5) and use the provided `log()` function to log it onto the page.
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### Types, Interfaces, and Classes
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Create inside `index.ts`:
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1. a type alias for string union type describing the states of Red-Green-Yellow traffic light
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2. a class hierarchy of your favorite metaphor (e.g. family, autombiles, animals)
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3. describe an object type with an interface
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### Generic
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Inside `index.ts`, create a generic class for a `Stack<T>` complete with a typed `pop()` and `push()` methods
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Hint: the Javascript array already has `push()` and `pop()` implemented for you. That can be your backing store.
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Be sure to use the provided `log()` to show the functionality of `Stack<T>`
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### Spread and Destructure
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1. Note the following code in index.ts:
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```ts
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const obj1 = {
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first: 'who',
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second: 'what',
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third: 'dunno',
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left: 'why'
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};
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const obj2 = {
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center: 'because',
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pitcher: 'tomorrow',
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catcher: 'today'
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};
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```
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2. Now create a one-liner using the spread syntax `{...x, ...y}` to create a new variable that combines these two objects.
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3. Using the destructuring syntax to retrieve the values for `{first, second, catcher}` from this new object created in step (2).
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### Async / Await
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1. Note the following code in index.ts:
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```ts
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function makePromise() {
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return Promise.resolve(5);
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}
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```
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2. call `makePromise()` with the `await` syntax and log the results using the provided `log()` function
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3. create a new function that uses the `async` keyword to create an async function. Make an await call to `makePromise()` and return the results
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@@ -1,5 +1,19 @@
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<!DOCTYPE html>
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<html>
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<head>
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<style>
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* {
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margin: 0;
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outline: 0;
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}
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textarea {
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width: 100vh;
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height: 100vh;
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border: none;
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}
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</style>
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</head>
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<body>
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<div id="app"></div>
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</body>
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@@ -1,12 +0,0 @@
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async function fetchSomething() {
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const response = await fetch('http://localhost:3000/hello');
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return await response.text();
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}
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// Async functions always returns Promise
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fetchSomething().then(text => {
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console.log('hello ' + text);
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});
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// adding an export to turn this into a "module"
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export default {};
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@@ -1,23 +0,0 @@
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// Generics for classes
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class Stack<T = number> {
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private data: T[] = [];
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push(item: T) {
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this.data.push(item);
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}
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pop(): T {
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return this.data.pop();
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}
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}
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const numberStack = new Stack();
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const stringStack = new Stack<string>();
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// Generics for functions
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function reverse<T>(arg: T[]): T[] {
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// TODO: implement the logic to reverse the array
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return arg;
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}
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// adding an export to turn this into a "module"
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export default {};
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34
step2-01/exercise/src/index.ts
Normal file
34
step2-01/exercise/src/index.ts
Normal file
@@ -0,0 +1,34 @@
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const app = document.getElementById('app');
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const textarea = document.createElement('textarea');
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textarea.setAttribute('readonly', 'true');
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app.appendChild(textarea);
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function log(results: string) {
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textarea.innerText += results;
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}
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// Some setup code for exercises
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const obj1 = {
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first: 'who',
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second: 'what',
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third: 'dunno',
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left: 'why'
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};
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const obj2 = {
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center: 'because',
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pitcher: 'tomorrow',
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catcher: 'today'
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};
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function makePromise() {
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return Promise.resolve(5);
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}
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// Do the exercises here, output your results with "log()" function
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// ...
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log('hello world');
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(async () => {
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// Place your code for the async / await exercise here
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// ...
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})();
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@@ -1,19 +0,0 @@
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// Interesting Typescript Topics
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// types
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import './types';
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// interface
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import './interfaces';
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// modularity
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import './modules';
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// generics
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import './generics';
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// await / async
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import './async';
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// spread syntax
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import './spread';
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@@ -1,22 +0,0 @@
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interface Car {
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make: string;
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model: string;
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}
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class MyCar implements Car {
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make: 'Honda';
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model: 'Accord';
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}
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const myCar: Car = {
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make: 'Honda',
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model: 'Accord'
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};
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// Interface as Functions
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interface InterestingFn {
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(someArgs: string): number;
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}
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// adding an export to turn this into a "module"
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export default {};
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@@ -1,3 +0,0 @@
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export default class DefaultClass {
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hello = 'world';
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}
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@@ -1,19 +0,0 @@
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import { namedConst, namedFn, namedObj, namedConstBracket, namedConst as c } from './named';
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import * as named from './named';
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// Print out the exports
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console.log(namedConst);
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console.log(c);
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console.log(namedFn());
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console.log(namedObj);
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console.log(namedConstBracket);
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// Print out exports through module level import
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console.log(named.namedConst);
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console.log(named.namedFn());
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console.log(named.namedObj);
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console.log(named.namedConstBracket);
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import DefaultClass from './default';
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console.log(new DefaultClass().hello);
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@@ -1,12 +0,0 @@
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export const namedConst = 5;
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export function namedFn() {
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return 5;
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}
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export const namedObj = {
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hello: 'world'
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};
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const namedConstBracket = 10;
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export { namedConstBracket };
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@@ -1,15 +0,0 @@
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// Destructuring
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var [x, y, ...rest] = [1, 2, 3, 4];
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console.log(x, y, rest); // 1,2,[3,4]
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// Array assignment
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var list = [1, 2];
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list = [...list, 3, 4];
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console.log(list); // [1,2,3,4]
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// Object assignment
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const point2D = { x: 1, y: 2 };
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const point3D = { ...point2D, z: 3 };
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// adding an export to turn this into a "module"
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export default {};
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@@ -1,55 +0,0 @@
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// Basic Types
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let isDone: boolean = false;
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let decimal: number = 6;
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let color: string = 'blue';
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let sky: string = `the sky is ${color}`;
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// Function Types
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type FibFn = (n: number) => number;
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// Object Types
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type Obj = {
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[key: string]: string;
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};
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// Object with Specified Keys
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type Specific1 = {
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foo: string;
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bar: number;
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common: string;
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};
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type Specific2 = {
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alice: string;
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bob: number;
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common: number;
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};
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// composition
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type typeofObj = {
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foo: string;
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bar: number;
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obj: Specific1;
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};
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// union, intersection
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type Union = Specific1 | Specific2;
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type Intersection = Specific1 & Specific2;
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// casting
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let choose1 = <Specific1>{ common: '5' };
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// string literal union
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type CatStatus = 'alive' | 'dead' | 'both';
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// Classes
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class Animal {}
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// Illustration purposes only
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// In real apps, avoid inheritance if possible
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// noted exception: React.Component with react@<16.8.0
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class Cat extends Animal {}
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class Dog extends Animal {}
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// adding an export to turn this into a "module"
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export default {};
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@@ -1,6 +1,6 @@
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// Destructuring
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var [x, y, ...rest] = [1, 2, 3, 4];
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console.log(x, y, rest); // 1,2,[3,4]
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var [a, b, ...rest] = [1, 2, 3, 4];
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console.log(a, b, rest); // 1,2,[3,4]
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// Array assignment
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var list = [1, 2];
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@@ -11,5 +11,14 @@ console.log(list); // [1,2,3,4]
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const point2D = { x: 1, y: 2 };
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const point3D = { ...point2D, z: 3 };
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// Concat two objects
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const obj1 = { x: 1 };
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const obj2 = { y: 2 };
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const obj3 = { ...obj1, ...obj2 };
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// Destructuring object
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const { x } = obj3;
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// adding an export to turn this into a "module"
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export default {};
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@@ -26,12 +26,16 @@ type Specific2 = {
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};
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// composition
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type typeofObj = {
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type TypeOfObj = {
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foo: string;
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bar: number;
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obj: Specific1;
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obj1: Specific1;
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obj2: Specific2;
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};
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// Get types by property
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type Obj1Type = TypeOfObj['obj1'];
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// union, intersection
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type Union = Specific1 | Specific2;
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type Intersection = Specific1 & Specific2;
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