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88 lines
2.5 KiB
Markdown
88 lines
2.5 KiB
Markdown
# Step 2.1: Introduction to Typescript
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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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> HINT: fib(n) = fib(n - 1) + fib(n - 2); fib(n <= 1) = 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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