Hooks

Hooks exist at two levels:

• schema hooks, attached to the schema definition,
• model hooks, attached to a specific model instance.

import { M, model } from "mongster";

const userSchema = M.schema({
  email: M.string(),
  name: M.string(),
});

userSchema.pre("createOne", (ctx) => {
  return {
    doc: {
      ...ctx.doc,
      email: ctx.doc.email.toLowerCase(),
    },
  };
});

userSchema.post("find", (ctx) => {
  console.log(ctx.result.length);
});

const User = model("users", userSchema);

User.pre("modify", (ctx) => {
  return {
    ...ctx,
    filter: {
      ...ctx.filter,
      deletedAt: { $exists: false },
    },
  };
});

Supported group aliases

• save: insertOne, insertMany, createOne, createMany
• modify: updateOne, updateMany, findOneAndUpdate, replaceOne, findOneAndReplace, upsertOne
• remove: deleteOne, deleteMany, findOneAndDelete

Group aliases accept a union-shaped context that mirrors every operation in the group. Only the fields relevant to the current operation are populated. Returning a context from the hook replaces the operation args, just like per-operation hooks.

// Soft-delete pattern: filter out deleted docs on every write operation.
Todo.pre("modify", (ctx) => ({
  ...ctx,
  filter: { ...ctx.filter, deletedAt: { $exists: false } },
}));

Execution order

When both schema and model hooks are present, the order is:

1. model pre hook
2. schema pre hook
3. database operation
4. schema post hook
5. model post hook

Practical advice

• Use schema hooks for rules that belong to the data shape itself.
• Use model hooks for collection-specific behavior.
• Keep hook logic small and predictable, especially for write paths.