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Start your free trialYan Kozlovskiy
30,427 PointsWhy do we use prototypes in JavaScript?
I would like to know why we use prototypes. I understand that each time we create a new instance of a function, it'll create new space in memory. Are all elements attached to this prototype object? Why and when should we use something.prototype.somethingelse?
2 Answers
Steven Parker
231,072 PointsBasically, prototypes are a way of establishing properties and methods that will be inherited, or adding new properties and methods to an existing object or set of objects of a given type.
Now I realize that probably isn't much help in itself, but I found this article and discussion thread: JavaScript Prototype in Plain Language over at JavaScriptIsSexy.com that might be more enlightening.
jason chan
31,009 PointsWe use prototypes for inheritance.
Since javascript isn't a formal object oriented language. That's how we do inheritance.
function Person(first, last) {
console.log(this);
this.firstname = first;
this.lastname = last;
console.log("This function is invoked.");
}
// inheriting from Person constructor to create a new method getFullName
Person.prototype.getFullName = function() {
return this.firstname + ' ' + this.lastname;
}
var john = new Person('john', 'doe');
console.log(john.getFullName());
var jane = new Person('jane', 'doe');
Person.prototype.getFormalFullName = function(){
return this.lastname + ', ' + this.firstname;
}
console.log(john.getFormalFullName());
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain
// emca2015 you have to use babel to compile this to javascript. This more traditional way create classes and inheritance. This also is similar to typescript
"use strict";
// we create a class here a blue print using the keyword constructor and class
class Polygon {
constructor(height, width) {
this.height = height;
this.width = width;
}
}
// we extend or inherit from Polygon with new methods. Basically we just adding new functions to Polygon, but we creating a new object called Square.
class Square extends Polygon {
constructor(sideLength) {
super(sideLength, sideLength);
}
get area() {
return this.height * this.width;
}
set sideLength(newLength) {
this.height = newLength;
this.width = newLength;
}
}
var square = new Square(2);