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

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This article represents tips and code samples on How to create and instantiate a Class in NodeJS. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

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());

 

Ajitesh Kumar

Ajitesh Kumar

Ajitesh has been recently working in the area of AI and machine learning. Currently, his research area includes Safe & Quality AI. In addition, he is also passionate about various different technologies including programming languages such as Java/JEE, Javascript and technologies such as Blockchain, mobile computing, cloud-native technologies, application security, cloud computing platforms, big data etc.

He has also authored the book, Building Web Apps with Spring 5 and Angular.
Ajitesh Kumar

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