Example 1:

import mongoose from 'mongoose'

const itemSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
      trim: true,
      maxlength: 50
    },
    status: {
      type: String,
      required: true,
      enum: ['active', 'complete', 'pastdue'],
      default: 'active'
    },
    notes: String,
    due: Date,
    createdBy: {
      type: mongoose.SchemaTypes.ObjectId,
      ref: 'user',
      required: true
    },
    list: {
      type: mongoose.SchemaTypes.ObjectId,
      ref: 'list',
      required: true
    }
  },
  { timestamps: true }
)

itemSchema.index({ list: 1, name: 1 }, { unique: true })

export const Item = mongoose.model('item', itemSchema)

Example 2:

import mongoose from 'mongoose'

const listSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
      trim: true,
      maxlength: 50
    },
    description: String,
    createdBy: {
      type: mongoose.SchemaTypes.ObjectId,
      ref: 'user',
      required: true
    }
  },
  { timestamps: true }
)

listSchema.index({ user: 1, name: 1 }, { unique: true })

export const List = mongoose.model('list', listSchema)

Example 3:

import mongoose from 'mongoose'
import bcrypt from 'bcrypt'

const userSchema = new mongoose.Schema(
  {
    email: {
      type: String,
      required: true,
      unique: true,
      trim: true
    },

    password: {
      type: String,
      required: true
    },
    settings: {
      theme: {
        type: String,
        required: true,
        default: 'dark'
      },
      notifications: {
        type: Boolean,
        required: true,
        default: true
      },
      compactMode: {
        type: Boolean,
        required: true,
        default: false
      }
    }
  },
  { timestamps: true }
)

userSchema.pre('save', function(next) {
  if (!this.isModified('password')) {
    return next()
  }

  bcrypt.hash(this.password, 8, (err, hash) => {
    if (err) {
      return next(err)
    }

    this.password = hash
    next()
  })
})

userSchema.methods.checkPassword = function(password) {
  const passwordHash = this.password
  return new Promise((resolve, reject) => {
    bcrypt.compare(password, passwordHash, (err, same) => {
      if (err) {
        return reject(err)
      }

      resolve(same)
    })
  })
}

export const User = mongoose.model('user', userSchema)