Data types in Typescript

Primitive types

1. boolean: true/false

2. number: whole numbers and floating point values

3. string: text values like "TypeScript"

4. bigint: whole numbers and floating point values, but allows larger negative and positive numbers than the number type

5. symbol:  are used to create a globally unique identifier

6. null and undefined: are the same as null and undefined of Javascript respectively

Special types

1. any:

• is a type that disables type checking and effectively allows all types to be used

let anyValue: any
anyValue = 'Typescript';
anyValue = 1;
const length = unknownValue.length;
// No compilation error. (But you can get runtime error)

2. unknown:

• is a similar, but safer alternative to any.TypeScript will prevent unknown types from being used

let unknownValue: unknown;
unknownValue = 'Typescript';
unknownValue = 1;
const length = unknownValue.length;
// Typescript will throw error "TS18046: 'unknownValue' is of type 'unknown'."
// You need to use type-checking before we can do that with unknown type
if (typeof unknownValue === 'string'){
  const length = unknownValue.length;
}

3. never:

Typescript - never

4. void

• is used where there is no data. For example, if a function does not return any value
• you can only assign undefined to void (also null of you do not turn on strictNullChecks)

const doSomethingAndDoNotReturnValue = (): void => {
  console.log('A function do something but do not return any value');
};