Like JavaScript in TypeScript we use camelCase most times for variables. However for "interface", "type" and "enum" we use PascalCase


type Result = "success" | "failure"

enum PermissionCodes {
  SITE_ADMIN = 'SiteAdmin',
  ORG_LEADER = 'OrgLeader',
  ORG_ADMIN = 'OrgAdmin',
  ORG_MEMEBER = 'OrgMember',
  PROJECT_LEADER = 'ProjectLeader',
  PROJECT_ADMIN = 'ProjectAdmin',
  PROJECT_MEMBER = 'ProjectMember',
  MEMBER = 'Member',
}

interface Item {
  id: string;
  title: string;
  sections?: Section[];
}

When to use PascalCase

Standards

Use "interfaces" and "types" to describe your data. In this way you can avoid using the "any" type.

interface MemberPageProps{ 
  member: Member; 
  projects: Project[]
}

const MemberPage = (props: MamberPageProps){
  // code...
}

Avoid using the "any" type

"Number", "String", "Symbol", and "Object" are almost never need to be used. Instead use "number", "string", "boolean", and "symbol".

// Correct
const myFunction = (id: string) => {
  // code...
}

// Incorrect
const myFunction = (id: String) => {
  // code..
} 

Avoid using Non-primitive types

You do not have to explicitly type your variable in initialization and this is okay to do when it can inferenced.

// In both cases name is typed to "string".
let name = "John Doe"
let name: string = "John Doe"

Type Inference

Best Practices

enum PermissionCodes {
  SITE_ADMIN = 'SiteAdmin',
  ORG_LEADER = 'OrgLeader',
  ORG_ADMIN = 'OrgAdmin',
  ORG_MEMEBER = 'OrgMember',
  PROJECT_LEADER = 'ProjectLeader',
  PROJECT_ADMIN = 'ProjectAdmin',
  PROJECT_MEMBER = 'ProjectMember',
  MEMBER = 'Member',
}

user: User = { 
  name: 'John Doe'
  role: PermissionCodes.SITE_ADMIN
}

const updateOrgTitle = (user: User, title: string) => {
  if(user.role === PermissionCodes.SITE_ADMIN){
    orgTitle = title;
  }  
}

Use enums

interface Member {
  id: string
  email: string;
  name: string;
}

interface Project {
  id: string;
  title: string;
  leader: Member;
  admins?: Member[];
  members?: Member[];
}

Use Interfaces

interface Person {
  name: string;
}

interface Member extends Person {
  email: string;
  password: string;
} 

Extend Interfaces

Examples

TypeScript is a programming language that adds typing and interfaces to JavaScript. Here you will find Standards, Best Practices, and Examples for TypeScript