stampit API

stampit API

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Quick start

Last updated 2 months ago
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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

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, {
  props: {
    S3: require('aws-sdk').S3
  },
  methods: {
    upload({ fileName, stream }) {
      this.log.info({ fileName }, 'Uploading file')
      return this.s3instance.upload({ Key: fileName, Body: stream }).promise()
    }
  },
  init({ bucket }, { stamp }) {
    this.s3instance = new this.S3({ 
      apiVersion: '2006-03-01', 
      params: { Bucket: bucket || stamp.compose.configuration.bucket }
    })
  },
  conf: {
    bucket: process.env.UPLOAD_BUCKET
  },
  statics: {
    setDefaultBucket(bucket) {
      return this.conf({ bucket })
    }
  }
})

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 understand what other API there are.

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