TypeScript Flashcards

Question

What function methods does TypeScript support?

Answer 1

apply, call, and bind function add(a: number, b:number): number { return a + b } add.apply(null, [1. 2]) add.call(null, 1, 2) add.bind(null, 1, 2) // all evaluate to 3.

Answer 2

Use the 'type' keyword to define a function signature. type Log = (message: string, userId?: string) => void

Answer 3

Types with free type parameters, allowing flexibility with different data types. type Filter = {(array: T[]. f: (item: T) => boolean): T[]} T is a type parameter, a placeholder for the actual type that will be passed to the Filter type later.

Answer 4

Filters an array based on a predicate function that returns true/false.

Answer 5

Uses a type parameter T as a placeholder for the actual type.

Answer 6

Difference in when type T is instantiated: call-time for Filter1, definition-time for Filter2.

Answer 7

Takes an array of T and a function that converts T to U, returns an array of U. function map (array: T[], f: (item: T) => U): U[] { let result = [] for (let i = 0; i < array.length; i++) { result[i] = f(array[i]} } return result }

Answer 8

class Piece { type Colour = "Black" } class King extends Piece {}

Answer 9

private, protected, and public control access levels of class members. - private modifier allows access within the same class. - protected modifier allows access within the same class and subclasses. - public modifier allows access from any location.

Answer 10

Classes that cannot be instantiated directly and can have abstract methods, which are accessible to and implemented by concrete classes.

Answer 11

Defined in abstract classes, they must be implemented by concrete subclasses.

Answer 12

Methods tied to the class, not instances; can only access other static members.

Answer 13

Objects with the same structure are considered the same type. They can share methods per say. -In other languages if you define a function for zebras if you try use it on poodles, it won’t work because the type checker assumes that if you wanted to use the zebra trot method on the poodle you would’ve made it a zebra. -TypeScript is more relaxed: If we define a function that takes Zebra, it can also accept a Poodle, because structurally the two classes are similar.

Answer 14

You can define generic type parameters and use them throughout the class. Later on when type checking is run, the types will be instantiated.

Answer 15

Another way to define the types of objects. type Sushi = { calories: number tasty: boolean } is equivalent to: interface Sushi = { calories: number tasty: boolean }

Answer 16

Combine multiple types into one using '&'. Used for inheritance for classes in typescript: Type Sushi = Food & {salt: boolean}

Answer 17

An interface can extend another, inheriting and adding properties. interface sushi extends Food {salty: boolean}

Answer 18

TypeScript automatically combines multiple declarations with the same name. interface User { age: number} interface User { name: string } let a: User = { age: 24, name: anya}

Answer 19

Yes, and they can implement multiple interfaces. class Cat implements Animal, Feline { eat(food: string) { console.info('ate food')} }

Answer 20

They can be inferred at compile time

Answer 21

Typescript inference happens at compile time whereas with JavaScript inference happens at runtime.

Answer 22

let message: string = 'Hello, World!'; console.log(message);

Answer 23

tsc hello_world.ts - this creates a hello_world.js file node hello_world.js

Answer 24

Advanced object types can have optional properties, numeric property names and index signatures - c?: string // means c is an optional property of type string - [key: number] is an index signature, so any number of numeric keys are allowed

Answer 25

function greet(name: string) {return 'hello ' + name} //named function let greet2 = function(name, string) {return 'hello ' + name} //function expression let greet 3 = (name: string) => {return 'hello ' + name} //arrow function expression let greet 4 = (name: string) => 'hello ' + name //shorthand arrow function expression

TypeScript Flashcards

(49 cards)