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JavaScript Design Patterns for Coding Interviews

Challenge: Solution Review

Explore the solution to a challenge implementing the factory pattern in JavaScript. Understand how to use constructor functions like ToyDuck and ToyCar within a ToyFactory to create objects based on provided parameters. This lesson helps you apply creational design patterns to efficiently manage object instantiation in coding interviews.

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Solution #

Node.js
function ToyFactory() {
    this.toy = ToyDuck;
    this.createToy = function(toyChosen) {
        if (toyChosen.toyType == "duck") {
            this.toy = ToyDuck;
        } else if (toyChosen.toyType == "car") {
            this.toy = ToyCar;
        }
        return new this.toy(toyChosen);
    }
}
function ToyDuck(toyObj) {
    this.color = toyObj.color;
    this.price = toyObj.price;
}
function ToyCar(toyObj) {
    this.color = toyObj.color;
    this.price = toyObj.price;
    this.name = toyObj.name;
}
var toyFactory = new ToyFactory();
var car = toyFactory.createToy({
    toyType: "car",
    color: "blue",
    price: 12,
    name: "honda"
})
var car = toyFactory.createToy({
    toyType: "car",
    color: "blue",
    price: 12,
    name: "honda"
})
console.log(car)
console.log(car instanceof ToyCar)
var duck = toyFactory.createToy({
    toyType: "duck",
    color: "yellow",
    price: 5,
})
console.log(duck)
console.log(duck instanceof ToyDuck)

Explanation

The task was to create a function createToy, which instantiated either a ToyDuck or a ToyCar object.

We start by defining the constructor functions. Let’s take a look at them.

  • ToyDuck

    function ToyDuck(toyObj){
  this.color = toyObj.color;
  this.price = toyObj.price;
}

    It accepts a parameter toyObj, that is, the “toy object”, sets its color equal to toyObj.color and its price equal to toyObj.price.

  • ToyCar

    function
...