form-errors

A javascript object for aggregating user errors on forms.

Installation

npm install form-error

then

var FormError = require('form-error');

TODO: Make an AMD/browser global build and publish on bower

Usage

FormError doesn't help you validate your forms. It helps you aggregate the all the validation failures you find when your users inevitably make mistakes. You start by requiring it.

All methods below return an object that is an instanceof FormError. They all return new objects and have no other effects.

• FormError(field, message): returns object with field as its sole own property, and an array containing just message as its value.

• FormError.empty(): returns an empty object.

• FormError.fromObject(plainObject): returns a FormError with all of plainObject's properties. This is particularly useful when you want to combine your own validation failures with validation failures returned from libraries like sequelize.

• formErrorInstance.concat(otherInstance): returns a FormError that is the union of formErrorInstance and otherInstance. If both argument instances have the same property, that property in the result is the concatenation of the property values in the arguments.

  Eg: FormError('x', 'bad').concat(FormError('x', 'good')) is equivalent to FormError.fromObject({x: ['bad', 'good']})

Here's a bigger example illustrating how you might use this.

function validate(user){
  return (
    user.name ? FormError.empty() : FormError('name', 'must not be blank.')
  ).concat(
    isValidEmail(user.email) ? FormError.empty() : FormError('email', 'must be a valid email address.')
  ).concat(
    isOneOf(user.gender, ['male', 'female', 'both', 'neither', 'undead', 'other']) ?
      FormError.empty() :
      FormError('gender', 'must be one of "male", "female", "both", "neither", "undead", or "other."')
  ).concat(
    isOneOf(user.occupation, ['wizard', 'programmer', 'automoton', '']) ?
      FormError.empty() :
      FormError('occpupation', 'is not recognized.')
  ).concat(
    user.gender == 'undead' && user.occupation ?
      FormError('occupation', 'is not available for the undead.') :
      FormError.empty()
  );
}

validate({gender: 'undead', 'occupation': 'surrenderer'})
/* => FormError.fromObject({
        name: ['must not be blank.'],
        email: ['must be a valid email address.'],
        occupation: ['is not recognized.', 'is not available for the undead.']
      })
*/