the-thing-is

"…now you've got errors you can work with."

var the = require('the-thing-is')

var a_valid_user = {
  name: ['string'],
  address: {
    street1: ['present', 'string', {matches: /.*/}],
    street2: ['string'],
    city: ['present', 'string'],
    state: ['present', 'string', {matches: /^[A-Z]{2}$/}],
    zip: ['present', 'string', {matches: /^[0-9]{5}$/}]
  }
}

var user = {
  name: "Joe Bob",
  address: {
    street1: '123 Any St.',
    street2: '',
    city: 'Anytown',
    state: undefined,
    zip: 12345
  }
}

function checkUser() {
  if (the(user).is(a_valid_user)) {
    return true;
  } else {
    return the.last.error;
  }
}

checkUser(user)

// the.last.error
[
  { 'address.state': ['present'] },
  { 'address.zip': ['string'] }
]

the-thing-is uses is-too under the hood to perform the comparisons. See its README for a list of what's available.

How to Write Validation Rules

Array of Standards

If you've got a simple variable to check then use an array to describe what you're expecting. the-thing-is will run the subject through a series of standards that'll be evaluated in order.

If the variable fails to meet any of the standards, the error will be added to an array at the.last.error. No further tests will be run.

var whatYouExpect = ['present', 'integer', {greaterThan:0, lessThan:256}]

the(16).is(whatYouExpect) // true

the(640).is(whatYouExpect) // false

the.last.thing // 640
the.last.error // [{lessThan:256}]

Tree of Standards

var a_valid_user = {
  name: ['string'],
  address: {
    street1: ['present', 'string', {matches: /.*/}],
    street2: ['string'],
    city: ['present', 'string'],
    state: ['present', 'string', {matches: /^[A-Z]{2}$/}],
    zip: ['present', 'string', {matches: /^[0-9]{5}$/}]
  }
}

Trees can be made as deep as you want, and the-thing-is will walk through it all to tell you what it finds. Should the check fail, the path to the offending nodes on the tree are stored in the.last.error array.

As illustrated in the first example, checkUser(user) returns an array of objects where the keys refer to the invalid propertiest and their values are arrays of errors.

// the.last.error
[
  { 'address.state': ['present'] },
  { 'address.zip': ['string'] }
]

In english this means user.address.state was undefined, and user.address.zip wasn't a string.

Errors

When your subjects fail to live up to your standards then the-thing-is will list all of its failures.

Note:

• the-thing-is doesn't stop at the first error it finds. It'll describe all errors for all properties.
• If there are no errors, the.last.error will be an empty array.

// examples
the.last.error == []
the.last.error == ['number']
the.last.error == [{greaterThan:0}]
the.last.error == [{'foo.bar': ['number']}]
the.last.error == [{'foo.bar': ['number', {greaterThan:0}]}]
the.last.error == [{'foo.bar': ['number', {greaterThan:0}]}, {'foo.baz': ['number', {lessThan:256}]}]

Additionally, if you describe your object using standards that don't exist in is-too then the-thing-is will throw a TypeError.

the('thing').is('gonnaThrowUp')
// => TypeError("`gonnaThrowUp` isn't a valid comparison method.")