> For the complete documentation index, see [llms.txt](https://hemantajax-2.gitbook.io/mongoose-step-by-step/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hemantajax-2.gitbook.io/mongoose-step-by-step/schema.md).

# Schema

```javascript
npm install mongoose -S
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/myappdatabase');
```

## Simple Schema

```javascript
var mongoose = require('mongoose'); 
var Schema = mongoose.Schema; 
var customerSchema = new Schema({ 
    name:      String, 
    address:   String, 
    city:      String, 
    state:     String, 
    country:   String, 
    zipCode:   Number, 
    createdOn: Date, 
    isActive:  Boolean 
}); 

var simpleSchema = new Schema({ fieldName: SchemaType });
```

## Complex Schema

```javascript
var mongoose = require('mongoose'); 
var Schema = mongoose.Schema;

// parent customer schema... 
var customerSchema = new Schema({ 
    name: { first: String, last: String }, 
    address: [ addressSchema ], 
    createdOn: { type: Date, default: Date.now }, 
    isActive: { type: Boolean, default: true}
});

// child address schema... 
var addressSchema = new Schema({ 
    type: String, 
    street: String, 
    city: String, 
    state: String, 
    country: String, 
    postalCode: Number 
});
```

## Alowed Data Type

| Mongoose Schema Type | Javascript Data Type |
| -------------------- | -------------------- |
| String               | String               |
| Number               | Number               |
| Boolean              | Boolean              |
| Date                 | Object               |
| Buffer               | Object               |
| Mixed                | Object               |
| ObjectId             | Object               |
| Array                | Array(Object)        |

## Adding custom method

```javascript
var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var userSchema = new Schema({
    name: String,
    age: Number
});

userSchema.methods.dudify = function() {
  this.name = this.name + '-dude'; 
  return this.name;
};

// the schema is useless so far
// we need to create a model using it
var User = mongoose.model('User', userSchema);

// make this available to our users in our Node applications
module.exports = User;
```

## Using custom method

```javascript
var User = require('./app/models/user');

var user = new User({
  name: 'Hemant',
  age: 20
});

user.dudify(function(err, name) {
  if (err) throw err;

  console.log('Your new name is ' + name); // Hemant-dude
});

// call the built-in save method to save to the database
user.save(function(err) {
  if (err) throw err;

  console.log('User saved successfully!');
});
```

## Run a Function Before Saving

Here is the code to add to our Schema to have the date added to created\_at if this is the first save, and to updated\_at on every save

```javascript
// on every save, add the date
userSchema.pre('save', function(next) {
  // get the current date
  var currentDate = new Date();

  // change the updated_at field to current date
  this.updated_at = currentDate;

  // if created_at doesn't exist, add to that field
  if (!this.created_at)
    this.created_at = currentDate;

  next();
});
```