Pseudoclassical Instantiation (new keyword)

This note assumes familiarity with the following concepts:

1. Sharing methods between object instances using the Prototype property.
2. Creating objects that inherit properties from another object using Object.create when property access fails.
3. Building constructor functions using Prototypal instantiation.

function Animal(name, energy) {
  let animal = Object.create(Animal.prototype)
  animal.name = name
  animal.energy = energy
  return animal
}
 
Animal.prototype.eat = function(amount) {
  console.log(`${this.name} is eating.`)
  this.energy += amount
}
 
const leo = Animal("Leo", 10)

Pseudoclassical instantiation is a syntactic shortcut in JavaScript that leverages the new keyword to implicitly perform Object.create and return a new object whose prototype is set to the constructor’s prototype. This approach mimics classical object-oriented inheritance patterns while utilizing JavaScript’s prototypal underlying mechanism.

function Animal(name, energy) {
  // let this = Object.create(Animal.prototype)
  
  this.name = name
  this.energy = energy
  
  //return animal
}
 
Animal.prototype.eat = function (amount) {
  console.log(`${this.name} is eating.`)
  this.energy += amount
}
 
const leo = new Animal("Leo", 10)

Omitting the new keyword when instantiating an object with pseudoclassical instantiation results in neither the this object being allocated nor the implicit return triggered. This is because the new keyword is crucial for invoking the constructor function with the proper context and memory allocation.

function Animal(name, energy) {
  this.name = name
  this.energy = energy
}
 
const leo = Animal('Leo', 7)
console.log(leo) // undefined

References

• A Beginner’s Guide to JavaScript’s Prototype