SimpleTypes.md

TypeScript Simple Types

---

Simple Types are also called primitives

1. Main types :

   • string : used to store text values such as "student"
   • number : used to store whole numbers and floating point numbers
   • boolean : true or false

2. Less common primitives used in later versions of Javascript and TypeScript:

   • bigint : stores whole and floating point values, allowing larger positive and neagtive values
   • symbol : creates a globally unique identifier

Type Assignment

1. Explicit : the type is specified

let name : string = "Roland";

2. Implicit : TypeScript will infer the type based on the assigned value

let name  = "Roland";

Errors

When using implicit assignment, any future attemmpt to assign the same variable a value of a different type, an error will be thrown

let name = "Roland"; // inferred to type string
firstName = 20; // attempts to re-assign the value to a different type

Disabling Type checking

TypeScript may not always properly infer what the type of a variable may be. In such cases, it will set the type to any which disables type checking.

// Implicit any as JSON.parse doesn't know what type of data it returns so it can be "any" thing...
const json = JSON.parse("25");
// Most expect json to be an object, but it can be a string or a number like this example
console.log(typeof json);