NodeJS – How to Create & Instantiate a Class – Code Samples

Following are the key points described later in this article:

• How to Create a Class?
• How to Instantiate a Class?

How to Create a Class?

//  This is a Constructor function taking age and passport 
//  as the paramaters
function Person(age, passport) {
  this.age = age;
  this.passport = passport;
}
// Sets the age
// 
Person.prototype.setAge = function(age) {
    this.age = age;
};
// Checks whether the person is Adult based on the age
// 
Person.prototype.isAdult = function() {
    return this.age >= 18? true: false;
};
// Checks whether the person can have bank accounts 
// based on whether he/she is an adult
// 
Person.prototype.canHaveBankAccounts = function() {
    return this.isAdult()?true:false;
};
// Sets the passport status of the person
// 
Person.prototype.passportStatus = function(status) {
    this.passport = status;
};
// Checks whether the person has the passport
// 
Person.prototype.hasPassport = function() {
    return this.passport;
};
//  Sets the Person object to module.exports
// 
module.exports = Person;

How to Instantiate a Class?

Following code also demonstrates the following:

• Check the parameters passed to “node” command: The function used is “process.argv”. The first element is “node” command. The second element at index 1 is file name. Third element is first parameter passed to the “node” command.
• Exit the execution: The function used is “process.exit()”.

var Person = require("./Person.js");
// Checks whether minimum of 3 parameters have been entered
// 
if(process.argv.length <= 2) {
  console.log("You must pass the age of the person.");
  // Exists 
  process.exit();
}
// Creates the person using the constructor function
// 
var person = new Person(1, false);

console.log("Person is an adult is: " + person.isAdult());
console.log("Person can have bank account is: " + person.canHaveBankAccounts());
// Sets the age of the person
// 
person.setAge(process.argv[2]);

console.log("Person is an adult is: " + person.isAdult());
console.log("Person can have bank account is: " + person.canHaveBankAccounts());