Schema

A Mongster schema describes one collection shape. Define it once, then reuse it for runtime validation, inferred types, and index metadata.

Start with M.schema()

import { M } from "mongster";

const todoSchema = M.schema({
  title: M.string().min(1).max(200),
  completed: M.boolean().default(false),
  priority: M.number().enum([1, 2, 3]).default(2),
  tags: M.array(M.string()).default([]),
  ownerId: M.objectId().index(),
  archivedAt: M.date().optional(),
})
  .addIndex({ ownerId: 1, completed: 1 })
  .withTimestamps();

type Todo = M.infer<typeof todoSchema>;
type CreateTodo = M.inferInput<typeof todoSchema>;

withTimestamps configuration

withTimestamps() accepts an object that lets you rename or disable the managed fields.

const schema = M.schema({ name: M.string() }).withTimestamps({
  createdAt: "madeAt",
  updatedAt: false,
});

config.createdAt and config.updatedAt accept:

• true (the default) — keep the field with the name createdAt / updatedAt.
• false — drop the field from the inferred type and skip writing it.
• "customName" — rename the field.

When timestamps are enabled, Mongster automatically appends $currentDate: { updatedAt: true } to every update operation, and adds $currentDate: { createdAt: true } on upserts that actually insert a new document. See Updates for the operator details.

What the schema gives you

• runtime validation for creates and updates,
• a stored document type via M.infer,
• an input type via M.inferInput,
• field-level and collection-level index definitions,
• optional timestamps through withTimestamps().

Nested shapes stay explicit

import { M } from "mongster";

const userSchema = M.schema({
  profile: M.object({
    displayName: M.string().min(1),
    timezone: M.string().default("UTC"),
  }),
  logins: M.array(
    M.object({
      ip: M.string(),
      at: M.date(),
    }),
  ).default([]),
});

Practical advice

• Use M.object() for embedded documents instead of ad-hoc nested values.
• Put compound indexes on the schema with addIndex(). See Indexes for the full helper set.
• Use withTimestamps() for collections that naturally track lifecycle dates.
• Declare refs directly in the schema with M.objectId().ref(() => Model) when another collection is involved.