I am teaching a course that includes explaining functional JavaScript and I want to have a really good example of functional programming that is hopefully cleaner then non-functional. I want to convert the following switch statement to functional. I've made an example of that conversion myself, but hoping there is a simpler solution.
Here is the switch statement version:
let animalType = "Poodle";
switch (animalType) {
case "Poodle":
case "Beagle":
case "Bulldog":
console.log(animalType + " is a dog.");
break;
case "Bengal":
case "Siamese":
console.log(animalType + " is a cat.");
break;
default:
console.log(animalType + " is not a dog or cat.");
break;
}And here is what I came up with as functional that I'm not that happy about
const result = getAnimalType("Poodle");
console.log("result:" + result)
function getAnimalType(animal) {
function isDog(animal) {
const dogs = ["Poodle", "Beagle", "Bulldog"];
return dogs.includes(animal)
}
function isCat(animal) {
const cats = ["Bengal", "Siamese"];
return cats.includes(animal)
}
return isDog(animal)
? animal + " is a dog."
: isCat(animal)
? animal + " is a cat."
: animal + " is not a dog or cat.";
}You can use an object to map animal types to functions.
function dog(animalType) {
return animalType + " is a dog.";
}
function cat(animalType) {
return animalType + " is a cat.";
}
function other(animalType) {
return animalType + " is not a dog or cat.";
}
const typeMap = {
Poodle: dog,
Beagle: dog,
Bulldog: dog,
Bengal: cat,
Siamese: cat
};
function getAnimalType(animalType) {
let typeFun = typeMap[animalType] || other;
return typeFun(animalType);
}
console.log(getAnimalType("Poodle"));One option is an object indexed by dog or cat, whose values are arrays of animal types. This is easily extensible to additional animal types.
const animalNamesByType = {
dog: ["Poodle", "Beagle", "Bulldog"],
cat: ["Bengal", "Siamese"]
};
function getAnimalType(animal) {
const entry = Object.entries(animalNamesByType).find(
entry => entry[1].includes(animal)
);
return entry
? `${animal} is a ${entry[0]}`
: `${animal} is not in animalNamesByType`;
}
console.log(getAnimalType("Poodle"));You can create a really simple 3-line function for this
const dogs = ["Poodle", "Beagle", "Bulldog"];
const cats = ["Bengal", "Siamese"];
const getAnimalType = (animal) => {
if(dogs.includes(animal)) return `${animal} is a dog`
if(cats.includes(animal)) return `${animal} is a cat`
return `${animal} is not a dog or cat.`
}
const result = getAnimalType("Poodle");
console.log("result:" + result)