Arrays in Typescript | Chinese Rule of Eight

Typed Arrays – Arrays where each element is some consistent type of value.

const carMakers: string [] = ['ford', 'toyota', 'chevy'];

const dates = [new Date(), new Date()];

const carsByMake: string[][] = [

['f150', 'f151'],

['corolla'],

];

// Help with inference with extracting values

const car = carMakers[0];

const myCar = carMakers.pop();

carMakers.map((car: string) : string => {

return car.toUpperCase();

});

Multiple Types in Arrays

// Flexible types

const importantDates = [new Date(), '2030-10-10'];

importantDates.push('2030-10-10');

importantDates.push(new Date());

When to use Arrays?

When we want to represent a collection of records which some arbitrary sort order.
of same type.

https://stackoverflow.com/questions/49047886/whats-difference-between-array-and-tuple/49047969

Tuple vs Arrays

Tuple – A tuple is a grouping of unnamed, ordered values. Each value in a tuple does not need to be the same type.

Array An array is mutable collection. They are very efficient to create, but must always be a single type.

We have a literal object like this:

const drink = {

color: 'brown',

carbonated: true,

sugar: 40

}

// array of string | number | boolean

const pepsi = ['brown', true, 40];

// But we have to memorize that 1st is the color, 2nd is boolean, 3rd is number

// so we can't use array

// we use tuple

const pepsi: [string, boolean, number] = ['brown', true, 40];

// that way we get compile time checking

// pepsi[0] = 40; would give compile time error

type alias

type Drink = [string, boolean, number]; // create a tuple type

const MountainDew: Drink = ['yellow', true, 20];

const sprite: Drink = ['clear', true, 40];

const tea: Drink = ['brown', false, 0];

But Why Tuples!?

Here’s why we don’t really use it too much.

1	const carSpecs: [number, number] = [400, 33543];

It does not describe what those numbers mean. It is not descriptive.

Let’s use object instead. It is much more descriptive because we are forced to put in a key.

const carStats = {

horsepower: 400,

weight: 3354

}