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\',\         


        

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

I would do for a real check for empty strings, because 0 is falsy, but a value and not empty.

function validateFields(object, keys) {
    keys.forEach(function (k) {
        if (k in object) {
            console.log(k + ": " + object[k]);
            if (object[k] === '') {
                console.log(k + " exists but is empty");
            }
            return;
        }
        console.log(k + " doesn't exist in object");
    });
}

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

validateFields(info, fields);

Answer 3

I think that you should be more concerned about what's the proper way of checking for it, rather than the most elegant. I'll drop a link to a very good post from Todd Moto regarding this: Please, take a look

In short your code should look like this:

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

Note: Take care when checking it has value, many expressions in javasscript are falsy (eg. 0, false, etc.) but are valid values.