typescript

• used in build time, same as js for compile time
• structure:
• variables
• object
• union
• aliases
• query
• class
• generics
  • function of types

module

• CommonJS(CJS)
• require
• module.exports
• MJS(ES Modules)
• import
• export

Other options

casting

let temp = 2 as number

type

readonly

open interface

declare global {
  interface A {
    b: number;
  }
}

type query

keyof = object.keys typeof = get types of those values

function type

interface twonumbercalc { (a: number, b: number): number; }

const add: twonumbercalc = (a, b) => a + b;

void

• used to indicate that a function does not return a value

this

setup type as parameter of function, also set strictBindCallApply to true in tsconfig.json

generic type

• pass type as parameter to a type
• dynamic type

record

• obj's key and value

class

• private
• only can be accessed by this instance itself
• can't be accessed by subclass
• protected
• can be accessed by subclass

return type