Data Kinds (Type Annotations and Inference)

Typescript sets data-kinds through let and const.

• colon : is for setting data-kinds
• equals = is for assigning variables

Explicit (Annotations)

let counter: number;  // counter is set to accept only number-kinds (numeric data type)
const counter: number;

counter = 2; // computer allows 2 because it is a number
counter = 'This should error'; // computer rejects this because it is a string 

Implicit (Inference or Contextual)

let counter = 0;

function startCounter (max=100) { ... }

// Computer understands that event is a kind of MouseEvent because of click
document.addEventListener('click', function(event) { console.log(event.button) });

Setting different data-kinds:

Array

let names: string[];

names = ['Adam', 'Barry'];

Object

let user: {
	name: string,
	age: number
};


user = {
	name: 'John',
	age: '4'
};

names = ['Adam', 'Barry'];

Primitive Data Kinds

number bigint string boolean && || ! null undefined symbol

String Interpolations

'string ${var} string'