Validating Javascript Model

Question

I'm looking to create a model in JavaScript. Here is an example of the code that I have so far:

// Person model
function Person(firstName, age) {
 // Check first name
 if (firstName) {
 if (typeof firstName === 'string') {
 this.firstName = firstName;
 } 
 else throw new Error('The first name is not a string.');
 } 
 else throw new Error('First name is a required field.');
 // Check age
 if (age) {
 if (typeof age === 'number') {
 if (age < 0) {
 throw new Error('The age provided is a negative.');
 } 
 else {
 this.age = age;
 }
 } 
 else throw new Error('The age provided is not a number.');
 } 
 else throw new Error('Age is a required field.');
}
// Example usage
try {
 var joel = new Person('Joel', 30);
 console.log(joel);
} 
catch(err) {
 console.log(err.message);
}

Is this an idiomatic approach to the solution? And if so is there a way in which I can improve it?

• Esailija: Seems inflexible, sometimes one needs temporarily invalid objects

Answer 1

I prefer to create isValid() method instead of exceptions and getValidationErrors() to get array of all errors instead of one error message with exception.

var joel = new Person('Joel', 30);
if( ! joel.isValid() ) {
 console.log(joel.getValidationErrors());
}

Also you can create some validation function like

validate({
 name: {
 type: 'string'
 },
 age: {
 type: 'number',
 minValue: 0,
 maxValue: 150
 }
}, {
 name: firstName,
 age: age
});

Which will return array of errors. If array length is 0 then validation passed.