some mongoose pre handler to run before a query takes place with mongoDB

userModel.js

const bcrypt = require("bcryptjs")
const mongoose = require("mongoose")

// we need to design a schema first of all
const userSchema = new mongoose.Schema({
  name: {
    type: String
  },
  password: {
    type: String
  },
  email: {
    type: String
  }
})

userSchema.pre(
  "save",
  async function(next) {
    const user = this;
    
    // this happens before saving a document
    if (user.isModified("password")) {
      user.password = await bcrypt.hash(user.password, 8);
    }
    
    next();
  }
)

const User = mongoose.model("User", userSchema);

module.exports = User;

save is the method run by mongoose after which this pre thing triggers itself