Everyday Types for Enterprise Data

Model request payloads, database rows, DTOs, and UI view models with clear everyday TypeScript types.

34 min

3 sections

objects

arrays

unions

dto

01. Primitive Types That Matter

Section 1 of 3

Most enterprise bugs are not solved by advanced type tricks. They are solved by consistently typing IDs, money, dates, booleans, and external payloads. Use primitives deliberately and promote important primitives into domain types when they carry business meaning.

typescript

type InvoiceStatus = "draft" | "sent" | "paid" | "void";

type InvoiceSummary = {
  id: string;
  customerId: string;
  status: InvoiceStatus;
  totalCents: number;
  dueDateIso: string;
  isOverdue: boolean;
};

const summary: InvoiceSummary = {
  id: "inv_1001",
  customerId: "cus_42",
  status: "sent",
  totalCents: 254900,
  dueDateIso: "2026-07-31",
  isOverdue: false,
};

Exercise

Type a customer account summary

Practice

Create a type for a customer account card with id, legal name, plan, seats used, seat limit, renewal date, and risk level.

TypeScript 6 Enterprise Setup

Narrowing and Runtime Boundaries

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