Everyday Types

https://www.typescriptlang.org/docs/handbook/2/everyday-types.html

• Primitives:
  • string
  • number: no distinguish between int and float
  • boolean
• Array:
  • T[] or Array<T>
  • [T] is Tuples
• any: to skip type checking
  
• Type Annotations:
  • type after variable
  • automatically inferred
• Functions:
  • Parameter type: function greet(name: string)
  • Return type: function getNumber(): number
  • Return Promise type:
    async function getNumber(): Promise<number>
    
• Object Types:
  • Value with properties
  • Optional properties: marked with ?

• Union Types
  • A type formed from two or more other types
    id: number | string
  • An operation allowed only if valid for every member of the union -> type narrow

• Interfaces:
  • Another way to name an object type
  • Key distinction is that a type cannot be re-opened to add new properties vs an interface which is always extendable

• Type Assertion
  • Specify a type TS can’t know
  • Specify a more specific type
• Literal Types
  • Difference between let and const
  • Combining literals -> unions
• null and undefined
  • To signal absent or uninitialized value
  • strictNullChecks:
    • Need to test before using the method or property
  • Non-null assertion operator (Postfix !)
• Less common primitives
  • bigint: very large integer
  • symbol: a globally unique reference