Javascript - elegant way to check object has required properties

Question

I'm looking for an good / elegant way to validate that a javascript object has the required properties, so far this is what I have:

var fields = ['name','age','address'];
var info = {
  name: "John Doe",
  age: "",
  phone: "123-456-7890"
}


var validateFields = function(o, required_fields) {
  required_fields.forEach(function(field){
    if(o.hasOwnProperty(field)){
      if(o[field]){
        console.log(field + ": " + o[field]);
      }else{
        console.log(field + " exists but is empty");
      }
    }else{
      console.log(field + " doesn't exist in object");
    }
  });
}

validateFields(info, fields);

Is there a more efficient / elegant way of doing this in plain javascript?

EDIT: Ok so I'm glad I asked because I had completely missed a bunch of possible conditions like zero.

With elegance out the window, how is this for a validation function? Are there any other cases I should be checking for?

var fields = ['name','age','address'];
var info = {
  name: "John Doe",
  age: 0,
  address: false,
  phone: "123-456-7890"
}


var validateFields = function(o, required_fields, null_valid, zero_valid, empty_valid) {
  var invalid_fields = [];
  required_fields.forEach(function(field){
    if(field in o){
      switch(o[field]){
        case '':
          console.log(field + " exists but is empty");
          if(!empty_valid){
            invalid_fields.push(o[field]);
          }
          break;
        case undefined:
          console.log(field + " exists but is undefined");
          invalid_fields.push(o[field]);
          break;
        case null:
          console.log(field + " exists but is null");
          if(!null_valid){
            invalid_fields.push(o[field]);
          }
          break;
        case 0:
          console.log(field + " exists and the value is 0");
          if(!zero_valid){
          }
          invalid_fields.push(o[field]);
          break;
        default:
          console.log(field + ": " + o[field]);
          break;
      }
    }else{
      console.log(field + " doesn't exist in object");
      invalid_fields.push(o[field]);
    }
  });

  return invalid_fields;
}


var invalid = validateFields(info, fields, true, true, false);
console.log(invalid);
if(invalid.length >0){
  console.log("ERROR: Missing fields");
}else{
  console.log("Fields are valid");
}

Answer 1

If you want "elegant", what you're looking for is called a schema:

var schema = {
  name: function (value) {
    return /^([A-Z][a-z\-]* )+[A-Z][a-z\-]*( \w+\.?)?$/.test(value);
  },
  age: function (value) {
    return !isNaN(value) && parseInt(value) == value && value >= 18;
  },
  phone: function (value) {
    return /^(\+?\d{1,2}-)?\d{3}-\d{3}-\d{4}$/.test(value);
  }
};

var info = {
  name: "John Doe",
  age: "",
  phone: "123-456-7890"
};

function validate(object, schema) {
  var errors = Object.keys(schema).filter(function (key) {
    return !schema[key](object[key]);
  }).map(function (key) {
    return new Error(key + " is invalid.");
  });

  if (errors.length > 0) {
    errors.forEach(function (error) {
      console.log(error.message);
    });
  } else {
    console.log("info is valid");
  }
}

validate(info, schema);

To address @AndreFigueiredo's pedantry, you can also check if the object contains the property at all:

var schema = {
  name: function (value) {
    return /^([A-Z][a-z\-]* )+[A-Z][a-z\-]*( \w+\.?)?$/.test(value);
  },
  age: function (value) {
    return !isNaN(value) && parseInt(value) == value && value >= 18;
  },
  phone: function (value) {
    return /^(\+?\d{1,2}-)?\d{3}-\d{3}-\d{4}$/.test(value);
  }
};

schema.name.required = true;
schema.age.required = true;

var info = {
  // name: "John Doe",
  age: "",
  phone: "123-456-7890"
};

function validate(object, schema) {
  var errors = Object.keys(schema).map(function (property) {
    var validator = schema[property];
    
    return [property, !validator.required || (property in object), validator(object[property])];
  }).filter(function (entry) {
    return !entry[1] || !entry[2];
  }).map(function (entry) {
    if (!entry[1]) return new Error(entry[0] + " is required.");
    else return new Error(entry[0] + " is invalid.");
  });

  if (errors.length > 0) {
    errors.forEach(function (error) {
      console.log(error.message);
    });
  } else {
    console.log("info is valid");
  }
}

validate(info, schema);

---

Update

Here's a modernized solution using features from ECMAScript 6 edition including destructuring, arrow functions, Object.entries(), template literals, and for...of:

const schema = {
  name: value => /^([A-Z][a-z\-]* )+[A-Z][a-z\-]*( \w+\.?)?$/.test(value),
  age: value => parseInt(value) === Number(value) && value >= 18,
  phone: value => /^(\+?\d{1,2}-)?\d{3}-\d{3}-\d{4}$/.test(value)
};

let info = {
  name: 'John Doe',
  age: '',
  phone: '123-456-7890'
};

const validate = (object, schema) => Object
  .keys(schema)
  .filter(key => !schema[key](object[key]))
  .map(key => new Error(`${key} is invalid.`));

const errors = validate(info, schema);

if (errors.length > 0) {
  for (const { message } of errors) {
    console.log(message);
  }
} else {
  console.log('info is valid');
}

And the version that performs required and validate checks separately:

const schema = {
  name: value => /^([A-Z][a-z\-]* )+[A-Z][a-z\-]*( \w+\.?)?$/.test(value),
  age: value => parseInt(value) === Number(value) && value >= 18,
  phone: value => /^(\+?\d{1,2}-)?\d{3}-\d{3}-\d{4}$/.test(value)
};

schema.name.required = true;
schema.age.required = true;

let info = {
  // name: 'John Doe',
  age: '',
  phone: '123-456-7890'
};

const validate = (object, schema) => Object
  .entries(schema)
  .map(([key, validate]) => [
    key,
    !validate.required || (key in object),
    validate(object[key])
  ])
  .filter(([_, ...tests]) => !tests.every(Boolean))
  .map(([key, invalid]) => new Error(`${key} is ${invalid ? 'invalid' : 'required'}.`));

const errors = validate(info, schema);

if (errors.length > 0) {
  for (const { message } of errors) {
    console.log(message);
  }
} else {
  console.log('info is valid');
}

Answer 2

You can use https://github.com/jquense/yup to solve your problem.

import * as yup from 'yup';

let schema = yup.object().shape({
  name: yup.string().required(),
  age: yup.number().required().positive().integer(),
  address: yup.string().required(),
});

var info = {
  name: "John Doe",
  age: "",
  phone: "123-456-7890"
}

// check validity
schema
  .isValid(info)
  .then(function (valid) {
    valid; // => false
  });

This is doing a bit more than just checking for the existence of fields, it's also ensuring that the data type is correct e.g. that age is a non-negative number.