Quick start

Quick start
​Install the JavaScript module from the NPM registry.
npm i @stamp/it
# or
npm i stampit
Create an empty stamp.
const stampit = require('@stamp/it')
​
let Stamp = stampit() // creates new stamp
​Compose it with another stamp.
const HasLog = require('./HasLog')
​
Stamp = Stamp.compose(HasLog) // creates a new stamp composed from the two
Add default properties to it.
Stamp = Stamp.props({ // creates a new derived stamp
  S3: require('aws-sdk').S3
})
Add an initializer (aka constructor).
Stamp = Stamp.init(function ({ bucket }, { stamp }) { // creates a new derived stamp
  this.s3instance = new this.S3({ 
    apiVersion: '2006-03-01', 
    params: { Bucket: bucket || stamp.compose.configuration.bucket } // using configuration.bucket, see below
  })
})
Add a method.
Stamp = Stamp.methods({ // creates a new derived stamp
  upload({ fileName, stream }) {
    this.log.info({ fileName }, 'Uploading file') // .log property from the HasLog stamp
​
    return this.s3instance.upload({ Key: fileName, Body: stream }).promise() // see above
  }
})
Add a configuration.
Stamp = Stamp.conf({ // creates a new derived stamp
  bucket: process.env.UPLOAD_BUCKET
})
Add a static method.
Stamp = Stamp.statics({ // creates a new derived stamp
  setDefaultBucket(bucket) {
    return this.conf({ bucket })
  }
})
Make the .s3instance , .log, and .S3 properties private.
const Privatize = require('@stamp/privatize')
​
Stamp = Stamp.compose(Privatize) // creates a new derived stamp
Give it a proper name.
const FileStore = Stamp.compose({ name: 'FileStore' })
Create objects from your stamp.
const store = FileStore()
Shorter API
Here is the same FileStore stamp but written in a more concise way.
S3FileStore.js
const HasLog = require('./HasLog')
const Privatize = require('@stamp/privatize')
​
const FileStore = HasLog.compose(Privatize, {
  name: 'FileStore',
  props: {
    S3: require('aws-sdk').S3
  },
  init({ bucket }, { stamp }) {
    this.s3instance = new this.S3({ 
      apiVersion: '2006-03-01', 
      params: { Bucket: bucket || stamp.compose.configuration.bucket }
    })
  },
  methods: {
    upload({ fileName, stream }) {
      this.log.info({ fileName }, 'Uploading file')
      return this.s3instance.upload({ Key: fileName, Body: stream }).promise()
    }
  },
  conf: {
    bucket: process.env.UPLOAD_BUCKET
  },
  statics: {
    setDefaultBucket(bucket) {
      return this.conf({ bucket })
    }
  }
})
The reusable HasLog stamp can be implemented in the following way.
HasLog.js
module.exports = require('@stamp/it')({
  init(_, { stamp }) {
    // this will reuse the stamp name "FileStore" we set above
    this.log = require('bunyan').createLogger({ name: stamp.name })
  }
})
Using the stamp
Use your stamp ad-hoc.
async function uploadTo(req, res) {
  const fileStore = FileStore({ bucket: req.params.bucket }) // create instance
​
  await fileStore.upload({ fileName: req.query.file, stream: req }) // use the method of the stamp
​
  res.sendStatus(201)
}
Or preconfigure it.
const CatGifStore = FileStore.setDefaultBucket('cat-gifs') // pre-configuring the bucket name
​
const catGifStore = CatGifStore() // create an instance of the store
​
await catGifStore.upload({ fileName: 'cat.gif', stream: readableStream })
If you want to silence the shameful fact that you are collecting cat gifs then here is how you disable log. Just overwrite the log property with a silent one.
const SilentCatGifStore = CatGifStore.props({
  log: {
    info() {} // silence!
  }
})
​
await SilentCatGifStore().upload({ fileName: 'cat.gif', stream: readableStream })
Alternatively, you can have a generic silent logger stamp. Compose with it to override the HasLog.
const HasSilentLog = stampit.props({ log: { info: () => {} } })
​
const SilentCatGifStore = CatGifStore.compose(HasSilentLog)
The new keyword also works with any stamp.
const catGifStore = new CatGifStore()
Another way to create an object is to use .create() static method.
const catGifStore = CatGifStore.create()
Mocking I/O in unit tests
Replacing actual S3 with a fake one.
const MockedFileStore = FileStore.props({
  S3() {
    return {
      upload() {
        return { promise() { return Promise.resolve() } }
      }
  }
})
​
// Same as above but a one-liner:
​
const MockedFileStore = FileStore.props({
  S3: () => ({ upload: () => ({ async promise() {} }) })
})
Basic API
Head to the Basics page to view more API documentation. However, by now you already know all you need.
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