# Methods

You can add methods (aka *functions*) to the objects created from your stamps.

```javascript
const Logger = stampit({
  methods: {
    debug(str) {
      console.log(str)
    }
  }
})

const logger = Logger()

logger.debug('Server started')
```

All the methods are **attached to object's prototype**.

```javascript
logger.__proto__.debug === Logger.compose.methods.debug
```

Moreover, the entire `methods` [descriptor metadata](https://stampit.js.org/essentials/what-is-a-stamp#stamps-metadata-descriptor) becomes the prototype.

```javascript
logger.__proto__ === Logger.compose.methods
```

If you compose the stamp above with any other stamp, then object instances created from it will also have the `.debug` method.

```javascript
const Server = Logger.compose({
  methods: {
    async start() {
      this.debug('Server started')
    }
  }
})

const server = Server()

server.debug('Starting server')
server.start()
```

## Descriptor merging algorithm

The methods are copied **by assignment**. In other words - **by reference** using `Object.assign`.

```javascript
Logger().debug === Server().debug
```

In case of conflicts the last composed method wins. To avoid method collision use the [@stamp/collision](https://stampit.js.org/ecosystem/stamp-collision) stamp. To make sure a method is implemented use the [@stamp/required](https://stampit.js.org/ecosystem/stamp-required) stamp.

> *NOTE*
>
> When using the [@stamp/required](https://stampit.js.org/ecosystem/stamp-required) stamp it creates a proxy object and returns from the factory. This means that `logger.__proto__ === Logger.compose.methods` or `logger.__proto__.debug === Logger.compose.methods.debug` will no longer be `true`.

## Other ways to add methods

Exactly the same stamp can be created in few ways. Here they all are.

```javascript
function myDebug(str) {
  console.log(str)
}

const Logger = stampit({
  methods: {
    debug: myDebug
  }
})

const Logger = stampit.methods({
  debug: myDebug
})

const Logger = stampit().methods({
  debug: myDebug
})
```