Form Objects: Example of Validator Object

formObjects3.js

var _ = require('underscore')

var NewStudentFormValidator = function() {
  this.errors = [] // for storing validation errors encountered
}

NewStudentFormValidator.prototype = _.extend(NewStudentFormValidator.prototype, {
  
  validate: function(data) {
    // call each validation method, storing
    // any errors on the this.errors array
    _.compose(
      this.validateFirstName,
      this.validateLastName,
    ).call(this, data)

    return this
  },

  // predicate identifying valid status
  // based on this.errors.length
  isValid: function() {
    return this.errors.length === 0
  },

  validateFirstName: function(data) {
    if (_.isUndefined(data.firstName)) {
      this.errors.push(new Error('first name is required'))
    }
    return data
  },

  validateLastName: function(data) {
    if (_.isUndefined(data.lastName)) {
      this.errors.push(new Error('last name is required'))
    }
    return data
  }

})