Deal

An object validator for domain-driven design.

Named after Deal, a Grateful Dead song first performed in 1971. Its about an experienced gambler, but (and this is a stretch) its first verse could apply to domain-driven design.

Since it cost a lot to win
and even more to lose
You and me bound to spend some time
wondring what to choose

My favorite performance was on February 26, 1977 at the Swing Auditorium in San Bernardino, CA.

Example Usage

var d = require('deal-validator');

> var createSong = d.define({
  artist: [d.required, d.string],
  title: [d.required, d.string],
  year: [d.optional, d.number]
});

// Given valid input, a valid object is returned
> createSong({
  artist: 'Grateful Dead',
  title: 'Deal'
});
{ artist: 'Grateful Dead', title: 'Deal' }

// If any of the validations fail, an error is thrown
> createSong({ title: 'Deal' });
Error: value cannot be undefined
    at required (/Users/ryanaghdam/Desktop/deal/index.js:28:13)
    at /Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:6122:33
    at f1 (/Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:166:27)
    at XWrap.reducer [as f] (/Users/ryanaghdam/Desktop/deal/index.js:9:45)
    at XWrap.@@transducer/step (/Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:701:25)
    at _arrayReduce (/Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:4148:46)
    at _reduce (/Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:4178:24)
    at Object.f3 [as reduce] (/Users/ryanaghdam/Desktop/deal/node_modules/ramda/dist/ramda.js:266:24)
    at /Users/ryanaghdam/Desktop/deal/index.js:18:16
    at repl:1:1

// Any attributes not defined in the schema are ignored
> createSong({
  artist: 'Grateful Dead',
  title: 'Playing in the Band',
  ruinedByDonna: true
});
{ artist: 'Grateful Dead', title: 'Playing in the Band' }

// Custom validator
var nonEmptyArray = function (value) {
  // validate that the input is an array
  value = d.array(value);

  if (value.length === 0) {
    throw new Error('array cannot be empty');
  }

  return value;
}

// Custom validators, using composition
var nonEmpty = function (value) {
  if (value.length === 0) {
    throw new Error('cannot be empty');
  }

  return value;
}

var nonEmptyArray = R.compose(nonEmpty, d.array);

var creator = d.define({
  p: [nonEmptyArray, d.required]
});

API

The following is a list of exported functions.

define(schema)

Returns a function that validates against the given schema.

Validators

Validators accept a single value and return it if it passes the validator. If it fails, an error is thrown.

optional(value)

Returns the given value. This function is purely syntactic; it allows for optional fields to be explicitly defined as such.

required(value)

Returns the given value if it is not undefined. Throws an error if it is undefined.

string(value)

Returns the given value if it is a string. An empty string is considered valid input.

boolean(value)

Returns the given value if it is a boolean or undefined. An error is thrown if the input is not a boolean.

number(value)

Returns the given value if it is a number or undefined. Infinity, -Infinity, and NaN are not considered valid input.

function(value)

Returns the given value if it is function or undefined.

array(value)

Returns the given value if it is an array or undefined. An empty object is considered valid input.

object(value)

Returns the given value if it is an object or undefined. An empty object is considered valid input.

Planned Enhancements

• Support schemas with nested objects
• Support custom error messages