acdc
JavaScript object transformation
Last updated 2 years ago by cressie176 .
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AC/DC

AC/DC is a library for transforming one JavaScript object into another. We wrote it because we needed to transform an horribly complicated legacy feed into something sane. It might also be useful for generating view models.

The Concepts

AC/DC works on the concept of flows of asynchronous tasks. The output from one task becomes the input for the next. The first task in a flow is implicitly set by AC/DC and will wrap the remaining tasks in a domain. The first explicit task in a flow will usually be a 'sequence', which will execute a collection of other tasks. For example...

Given a customer

{
    "details": {
        "title": "Mr",
        "firstName": "Fred",
        "lastName": "Bloggs",
        "dateOfBirth": "2015-07-15T00:00:00.000+01:00"
    }
}
domain()
└── sequence()
    ├── output(customer)           // Yields the customer object
    ├── get('details.dateOfBirth') // Yields '2015-07-15T00:00:00.000+01:00'
    └── parseDate()                // Yields a JavaScript date object representing '2015-07-15T00:00:00.000+01:00'

To operate on multiple properties of an object use the fork task

domain()
└── sequence()
    ├── output(customer)             // Yields the customer object
    ├── fork()
    │   ├── get('details.title')     // Yields 'Mr'
    │   ├── get('details.firstName') // Yields 'Fred'
    │   └── get('details.lastName')  // Yields 'Bloggs'
    └── format('%s. %s %s')          // Yields 'Mr. Fred Bloggs'

For richer transformations use combinations of sequences, forks, get and set

domain()
└── sequence()
    ├── output(customer)
    ├── fork()
    │   ├── sequence()
    │   │   ├── get('details.dateOfBirth')
    │   │   ├── parseDate()
    │   │   └── set('dob')
    │   ├── sequence()
    │   │   ├── get('details.title')
    │   │   └── set('title')
    │   ├── sequence()
    │   │   ├── get('details.firstName')
    │   │   └── set('firstName')
    │   ├── sequence()
    │   │   ├── get('details.lastName')
    │   │   └── set('lastName')
    │   └── sequence()
    │       ├── render('{{details.title}}. {{details.firstName}} {{details.lastName')
    │       └── set('fullName')
    └── merge()

Yields

{
    title: 'Mr',
    firstName: 'Fred',
    lastName: 'Bloggs',
    fullname: 'Mr. Fred Bloggs',
    dob: Date<2015-07-15T00:00:00.000+01:00>
}

All of this gets a bit verbose, and could be more tersely written as

domain()
└── sequence()
    ├── output(customer)
    ├── fork()
    │   ├── transform('details.dateOfBirth', parseDate(), 'dob')
    │   ├── copy('details.title', 'title')
    │   ├── copy('details.firstName', 'firstName')
    │   ├── copy('details.lastName', 'lastName')
    │   └── sequence()
    │       ├── render('{{details.title}}. {{details.firstName}} {{details.lastName')
    │       └── set('fullName')
    └── merge()

The Code

var acdc = require('acdc')
var tasks = require('acdc/lib/tasks')
var sequence = tasks.flow.sequence
var output = tasks.flow.output
var fork = tasks.flow.fork
var copy = tasks.property.copy
var transform = tasks.property.transform
var parseDate = tasks.date.parseDate
var merge = tasks.array.merge
var render = tasks.hogan.render

acdc()
    .run((dsl, cb) => {
        cb(sequence([
            output(customer),
            fork([
                transform('details.dateOfBirth', parseDate(), 'dob'),
                copy('details.title', 'title'),
                copy('details.firstName', 'firstName'),
                copy('details.lastName', 'lastName'),
                sequence([
                    render('{{details.title}}. {{details.firstName}} {{details.lastName}}'),
                    set('fullName')
                ])
            ]),
            merge()
        ]))
    })
    .done(done)

The DSL

If you're not opposed to using with you can reduce the number of imports as follows

var acdc = require('acdc')
var tasks = require('acdc/lib/tasks')

acdc()
    .bind(tasks.flow),
    .bind(tasks.property),
    .bind(tasks.date),
    .bind(tasks.array),
    .bind(tasks.hogan)
    .run((dsl, cb) => {
        with(dsl) {
            cb(sequence([
                output(customer),
                fork([
                    transform('details.dateOfBirth', parseDate(), 'dob'),
                    copy('details.title', 'title'),
                    copy('details.firstName', 'firstName'),
                    copy('details.lastName', 'lastName'),
                    sequence([
                        render('{{details.title}}. {{details.firstName}} {{details.lastName}}'),
                        set('fullName')
                    ])
                ]),
                merge()
            ]))
        }
    })
    .done(done)

Provided Tasks

AC/DC provides scores of tasks for transformation and flow control. The most important ones are in the flow, logic and property folders. For further information please consult the Task API

Custom Tasks

A simple task is an object with a 'fn' property of type function. We refer to this object as the task definition.

module.exports = {
    fn: function uppercase(input, ctx, cb) {
        cb(null, input ? input.toUpperCase() : input)
    }
}

You can validate the input by adding a schema property

var Joi = require('joi')
var schemas = require('acdc/lib/schemas')

module.exports = {
    fn: function uppercase(input, ctx, cb) {
        cb(null, input ? input.toUpperCase() : input)
    },
    schema: schemas.context.keys({
        input: Joi.string().allow('').optional()
    })
}

Before using your custom task in a flow you need to shorthand it. This will convert the task it into an executable function and copy function arguments to ctx.params. If your task uses parameters, you must include a schema which validates the parameters since this will also determine argument position to parameter mapping.

Flow Definition

var customTaskDef = require('../my/custom/task')
var shorthand = require('acdc/lib/utils/shorthand')
var customTask = shorthand(customTaskDef)

acdc()
    .bind(tasks.flow),
    .bind(tasks.property)
    .run((dsl, cb) => {
        with(dsl) {
            cb(sequence([
                output(customer),
                get('details.title'),
                customTask('Fred', 'Bloggs'),
                set('title')
            ]))
        }
    })
    .done(done)

Task Definition

var Joi = require('joi')
var _ = require('lodash')
var schemas = require('acdc/lib/schemas')
var R = require('ramda')

module.exports = {
    fn: function customTask(input, ctx, cb) {
        cb(null, ctx.params.firstName + ' ' + ctx.parmas.lastName)
    },
    schema: schemas.context.keys({
        params: Joi.object().keys({
            firstName: Joi.string(),
            lastName: Joi.string(),
        })
    })
}

Custom Task Libraries

If you write lots of custom tasks you may want to organise them into libraries and require them en masse. See acdc/utils/requireTasks and index.js in any of the provided tasks folders for how to do this.

Inline Tasks

You can add tasks inline as follows...

acdc()
    .bind(tasks.flow),
    .bind(tasks.property)
    .run((dsl, cb) => {
        with(dsl) {
            cb(sequence([
                output(customer),
                get('details.title'),
                {
                    task: {
                        fn: function uppercase(input, ctx, cb) {
                            cb(null, input ? input.toUpperCase() : input)
                        }
                    }
                },
                set('title')
            ]))
        }
    })
    .done(done)

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