Express form validation #nodejs

form.js

//// form -- form validation
///
/// Represent the structure of a form and use it to validate form
/// data.  Here's a Form that describes a create-account form:
///
///   var SignupForm = form.Form('Sign Up')
///    .text('account', 'Account Name', form.required(/[\w-\.]+/))
///    .email('email', 'Email', form.required())
///    .password('password', 'Password', form.required())
///    .password('confirm', 'Confirm', [form.required(), form.equal('password')]);
///
/// Each field has a name, title, and validator or sequence of
/// validators.  It's easy to make custom validators; see the
/// "Validators" section at the end of this file.
///
/// The form above ius used by this view to process request data
/// before creating an account:
///
///   app.post('/account', function(req, res) {
///     var result = SignupForm.validate(req.body);
///     if (!result.isValid())
///       return res.send(result.errors(), 400);
///
///     var data = result.data,
///         profile = { email: data.email };
///
///     db.newAccount(data.account, data.password, profile, function(err, key) {
///       if (err)
///         res.send(err.toString(), 500);
///       else if (!key)
///         res.send([{ account: "This account already exists" }], 400);
///       else {
///         var uri = '/account/' + key.id;
///         res.send({ uri: uri }, { Location: uri }, 201);
///       }
///     });
///   });
///

exports.Form = Form;
exports.Field = Field;
exports.required = required;
exports.equal = equal;


/// --- Form

// A form is a sequence of fields.  Fields participate in the
// validation process.

function Form(title) {
  if (!(this instanceof Form))
    return new Form(title);

  this.title = title;
  this.fields = {};
  this.fieldList = [];

  return this;
}

Form.prototype.text = field;
Form.prototype.password = field;
Form.prototype.email = field;

function field(name, title, valid) {
  var field = new Field(name, title, wrapArray(valid));
  this.fields[name] = field;
  this.fieldList.push(field);
  return this;
}

Form.prototype.validate = function validate(data) {
  var form = this,
      valid = new Validation(this, data),
      value;

  this.fieldList.forEach(function(field) {
    try {
      field.validate(valid);
    } catch (exn) {
      if (!(exn instanceof Invalid))
        throw exn;
      valid.errorList.push(exn);
    }
  });

  return valid;
};


/// --- Fields

// A field has a name, title, and sequence of validators.

function Field(name, title, valid) {
  this.name = name;
  this.title = title;
  this.valid = valid;
}

Field.prototype.validate = function validate(valid) {
  valid.data[this.name] = this.validValue(valid.input[this.name], valid);
};

Field.prototype.validValue = function _validate(value, valid) {
  var field = this,
      result;

  this.valid.forEach(function(validator) {
    result = validator.call(field, value, valid);
    if (result !== undefined)
      value = result;
  });

  return value;
};


/// --- Validation

// When Form.validate() is called, a validation state is created.
// This state is used to track the valid data and any errors.

function Validation(form, input) {
  this.form = form;
  this.fields = form.fields;
  this.input = input;
  this.data = {};
  this.errorList = [];
}

Validation.prototype.isValid = function isValid() {
  return this.errorList.length == 0;
};

Validation.prototype.fail = function fail(field, reason) {
  throw new Invalid(field, reason);
};

Validation.prototype.errors = function errors(fn) {
  return this.errorList.map(fn || function(item) {
    return { name: item.field.name, reason: item.toString() };
  });
};

function Invalid(field, reason) {
  this.field = field;
  this.reason = reason;
}

Invalid.prototype.toString = function() {
  return '"' + this.field.title + '" ' + this.reason + '.';
};


/// --- Validators

// A validator is called in the context of a field and is passed the
// field's value and the validation state.  If a validator returns a
// value, that value is used as the new field value.  If validation
// fails, valid.fail(this, "reason") should be returned.

function required(pattern) {
  pattern = pattern || /\S+/;
  return function required(value, valid) {
    if (!value)
      return valid.fail(this, 'is required');
    else if (!pattern.test(value))
      return valid.fail(this, "isn't formatted correctly.");
  };
}

function equal(name) {
  return function equal(value, valid) {
     if (value != valid.input[name])
      return valid.fail(this, 'must match "' + valid.fields[name].title + '"');
  };
}


/// --- Aux

function wrapArray(value) {
  if (value instanceof Array)
    return value;
  return (value === undefined) ? [] : [value];
}

test-form.js

//// Test form.js
///
/// Install Vows <http://vowsjs.org/>, and form.js, then run:
///
///   vows test-form.js
///

var assert = require('assert'),
    sys = require('sys'),
    form = require('form'),
    vows = require('vows');

var SignupForm = form.Form('Sign Up')
  .text('account', 'Account Name', form.required(/[\w-]+/))
  .email('email', 'Email', form.required())
  .password('password', 'Password', form.required())
  .password('confirm', 'Confirm', [form.required(), form.equal('password')]);

vows.describe('Form').addBatch({
  'With valid data,': {
    topic: function() {
      return SignupForm.validate({
        account: 'some-user',
        email: '[email protected]',
        password: 'foo',
        confirm: 'foo',
        junk: 'bar'
      });
    },

   'the result': {
     'is valid': function(topic) {
       assert.ok(topic.isValid());
     },

     'has no errors': function(topic) {
       assert.deepEqual(topic.errors(), []);
     },

     'contains valid data': function(topic) {
       assert.deepEqual(topic.data, {
         account: 'some-user',
         email: '[email protected]',
         password: 'foo',
         confirm: 'foo'
       });
     }
   }
  },

  'But for invalid data,': {
    topic: function() {
      return SignupForm.validate({
        account: '[email protected]',
        password: 'foo',
        confirm: 'goo'
      });
    },

    'the result': {
      'is not valid': function(topic) {
        assert.ok(!topic.isValid());
      },

      'has errors': function(topic) {
        assert.deepEqual(
          topic.errors(message),
          ['"Email" is required.', '"Confirm" must match "Password".']
        );
      }
    }
  }
}).export(module);

function message(invalid) {
  return invalid.toString();
}