Course Understanding Typescript

• Is a javascript superset
• A language building up on Javascript
• Add new features + advantages to javascript
• Need to be compiled to javascript
• Compile typescript features to javascript workarounds
• Typescript only checks before compilation

Instaling and using typescript

npm i -g typescript

tsc fileName.ts
tsc fileName.ts --watch
tsc fileName.ts -w

Para dar watch em todos os arquivos typescript presentes no diretório atual use o comando, o qual criará um arquivo tsconfig.json que representa o arquivo de configuração do typescript (mesmo propósito que o package.json) Com isto é possivel rodar somente tsc -w para dar watch nos arquivos

tsc --init
tsc -w

Typescript Overview

Typescript adds:

• Types
• Next-gen Javascript Features (Compiled down for older Browsers)
• Non-Javascript Features like Interfaces or Generics
• Meta-Programming Features like Decorators
• Rich Configuration Options
• Modern Tooling that helps even in non-Typescript Projects

Core Types

Principal types from Typescript

In Typescript, you work with types like string or number Important: It is string and number (etc.), NOT String, Number, etc. The core primitive types in Typescript are all lowercase!

Core Type: number

All numbers, no differentiation between integers or floats

1, 5.3, -10

Core Type: string

All text values

'Hi'
"Hi"
`Hi`

Core Type: boolean

Just these two, no "truthy" or "falsy" values

true
false

Core Type: object

Any Javascript object, more specific types (type of object) are possible

{
  age: 30
}

Core Type: Array

Any javascript array, type can be flexible or strict (regarding the element types)

[1, 2, 3]

Core Type: Tuple

Added by Typescript: Fixed-length array and fixed type

[1, 2]

Core Type: Enum

Added by Typescript: Automatically enumerated global constant identifiers

enum Type {
  NEW,
  OLD
}

enum Role {
  ADMIN = 5, // 5
  READ_ONLY, // 6
  AUTHOR,    // 7
}

enum File {
  JPG = 100,
  PDF = 200,
  EXE = 300,
}

enum Color {
  RED = 'Red'
  BLUE = 'Blue'
  Yellow = 'Yellow'
}

Core Type: Any

Any kind of value, no especific type assignment

Type Inference

Automatic understands what type a variable have when created with a core type

const number1 = 1
// Same as const number1: number = 1

Compiler