validator.js

model.js

validator = new Validator({
  presence: ['address', 'email', 'password', 'password_confirmation'],
  regex: {
    email: '[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}'
  },
  length: {
    password: '> 10',
    password_confirmation: '> 10'
  },
  custom: [
    function(obj){
      return [obj.password === obj.password_confirmation, 'passwords don\'t match'];
    },
  ]
});


validator.validate({password: 'hello', password_confirmation: 'world'});

validator.js

modules.exports = function(){
  class Validator{
    constructor(rules){
      this.rules = rules;
      this.errors = [];
    }
    
    validate(things){
      // validate presence
      this.errors = [];
      if(this.rules.presence && this.rules.presence.length > 0){
        for(let i=0;i<this.rules.presence.length;i++){
          if(!things[this.rules.presence[i]]){
            this.errors.push(this.rules.presence[i] + ' must be present');
          }
        }
      }
      // validate regex
      if (this.rules.regex){
        for(let x in this.rules.regex){
          if(things[x] && !things[x].match(this.rules.regex[x])){
            this.errors.push(x + ' is invalid');
          }
        }
      }
      
      // validate length
      if (this.rules['length']){
        for(let x in this.rules['length']){
          let [symbol, value] = this.rules['length'][x].split(' ')
          switch(symbol){
            case '=':
              if(!things[x].length === value){
                this.errors.push(x + ' must be ' + value + ' characters long');
                break;
              }
            case '>':
              if(!things[x].length > value){
                this.errors.push(x + ' must be greater than ' + value + ' characters');
                break;
              }
            case '<':
            if(!(things[x].length < value)){
                this.errors.push(x + ' must be less than ' + value + ' characters');
                break;
            }
          }
        }
      }
      
      //validate custom functions
      if (this.rules.custom && this.rules.custom.length > 0){
        for(let i=0;i<this.rules.custom.length; i++){
          let[test,msg] = this.rules.custom[i](things);
          if(!test){
            this.errors.push(msg);
          }
        }
      }
      
      // return errors if there are any
      if(this.errors){
        return this.errors ;
      }else{
        return null;
      }
    }
  }
  return Validator;
}