stampit API
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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
}
})
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.