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New

Often we need to create many similar objects. 
 
/**
 * The 'new' operator allows to create many similar objects
 * The regular {...} allows to create only one object
 * 
 * Any function can be run with new
 * The capital first letter is a convention
 * 
 * Private constructor (Singleton):
 * Encapsulate code that construct the object, 
 * without future reuse
 */

function User(name) {
    this.name = name;
    // this = {};   // implicit
    // return this; // implicit
}

let A = new User("Jack");
let B = new User("Mike");

let C = new function(name) { // Singleton
    this.name = "John";
    this.isAdmin = true;
}

console.log(A.name);        // Jack
console.log(B.name);        // Mike
console.log(C.isAdmin);     // true

Methods

We can add to this not only properties, but methods as well. 
 
/**
 * We can add methods to constructor
 * For more complex syntax, we will use classes
 * 
 * JavaScript provides constructor functions for many 
 * built-in language objects: like Date or Set
 */

function User(name, birthdate) {

    this.name = name;
    this.age = new Date().getFullYear() - new Date(birthdate).getFullYear();
    this.isAdult = this.age >= 18;
    this.show = () => {
        console.log(this.name + ' is adult: ' + this.isAdult);
    }
}

let user = new User("John", '01-01-1980');
user.show(); // John is adult: true



  Last update: 451 days ago