Functional instantiation is a pattern that involves creating a function which accepts one or more arguments to instantiate an object. This function is consistently used to construct an object, hence it is referred to as a “constructor function”.
Functional instantiation stems from the process of creating a simple object. While creating a single object is straightforward, it becomes inadequate when we need multiple objects that perform the same function.
let animal = {}
animal.name = 'Leo'
animal.energy = 10
animal.eat = function (amount) {
console.log(`${this.name} is eating.`)
this.energy += amount
}To implement functional instantiation, we can simply incorporate the code used to create a basic object into a constructor function. In our example, this is the Animal function that accepts two arguments: name and energy.
function Animal (name, energy) {
let animal = {}
animal.name = name
animal.energy = energy
// overallocating the memory when creating multiple instances
animal.eat = function (amount) {
console.log(`${this.name} is eating.`)
this.energy += amount
}
return animal
}
const leo = Animal('Leo', 7)
const snoop = Animal('Snoop', 10)Tip
It is recommended to capitalize the name of the constructor function. This convention helps other developers recognize it as a constructor function.
Shared Methods
You may observe that the eat function in our Animal constructor is repeatedly created for each object (leo and snoop) we instantiate.
To address this issue and minimize memory usage, we could extract all functions from the constructor function and place them in a separate object. Then, when we instantiate an object from the constructor, we can reference the function from the newly created object.
const animalMethods = {
eat(amount) {
console.log(`${this.name} is eating.`)
this.energy += amount
}
}
function Animal (name, energy) {
let animal = {}
animal.name = name
animal.energy = energy
animal.eat = animalMethods.eat
return animal
}
const leo = Animal('Leo', 7)
const snoop = Animal('Snoop', 10)References