I'm new to Javascript and learning about objects. I've learned that you can add a new property or method to an object with prototype.
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";
Now i'm wondering if it's also possible to add a new property with a new parameter without directly assigning the new property or changing the object constructor. So, it becomes:
function Person(first, last, age, eyecolor, nationality) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
this.nationality = nationality;
}
You can do this by wrapping the original constructor in a new function, like this:
const originalPerson = Person;
Person = function(first, last, age, eyecolor, nationality) {
const instance = new originalPerson(first, last, age, eyecolor);
instance.nationality = nationality;
return instance;
};
Live Example:
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
const originalPerson = Person;
Person = function(first, last, age, eyecolor, nationality) {
const instance = new originalPerson(first, last, age, eyecolor);
instance.nationality = nationality;
return instance;
};
const joe = new Person("Joe", "Bloggs", 42, "brown", "English");
console.log(joe.nationality);You can also do it via inheritance:
const originalPerson = Person;
Person = class extends originalPerson {
constructor(first, last, age, eyecolor, nationality) {
super(first, last, age, eyecolor);
this.nationality = nationality;
}
};
Live Example:
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
const originalPerson = Person;
Person = class extends originalPerson {
constructor(first, last, age, eyecolor, nationality) {
super(first, last, age, eyecolor);
this.nationality = nationality;
}
};
const joe = new Person("Joe", "Bloggs", 42, "brown", "English");
console.log(joe.nationality);In both of those cases I've reassigned Person, but you don't have to do that, you could just use ExtendedPerson or some such:
class ExtendedPerson extends Person {
constructor(first, last, age, eyecolor, nationality) {
super(first, last, age, eyecolor);
this.nationality = nationality;
}
}
...and then use new ExtendedPerson(/*...*/).
Live Example:
function Person(first, last, age, eyecolor) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eyecolor;
}
class ExtendedPerson extends Person {
constructor(first, last, age, eyecolor, nationality) {
super(first, last, age, eyecolor);
this.nationality = nationality;
}
}
const joe = new ExtendedPerson("Joe", "Bloggs", 42, "brown", "English");
console.log(joe.nationality);