This content originally appeared on DEV Community and was authored by Christian Falucho
Today's progress
Today I learned about functional programming.
What I learned
Functional programming is a style of programming in which solutions are simple. A function takes an input, processes it and returns an output.
Three important factors of functional programming:
- Isolated function - does not depend on outside variables (global variables)
- Pure functions - same input always give the same output
- Function has limited side effects - this means any changes or mutations is controlled.
This allows for greater control, less mutation or changing of variables and objects.
For instance, let's say we have a global variable called animals and stores an array of different animals.
let animals = ['lion', 'eagle', 'cheetah', 'bear', 'giraffe']
Let's create two functions. One function adds a new animal and the other function removes an animal.
// adds an animal to arr
function add(arr, animalName){
// make a copy of the array of animals
let newArr = [...arr]
// push new animal to new arr
newArr.push(animalName);
// return the new array
return newArr;
}
// removes an animal from arr
function remove(arr, animalName){
//make a copy of the array of animals
let newArr = [...arr]
// grab the index of the animal name
// store into variable
animal_index = newArr.indexOf(animalName)
// if the animal's index exist
// remove it, use splice
if(animal_index >= 0){
newArr.splice(0, 1)
}
// return the new array
return newArr;
}
You'll notice in the above code that we created two functions and in both functions take two parameters. The first parameter is the array and the second parameter takes in a string animal.
Inside the functions we added a line of code that makes a copy of the global array by passing it through our function argument function add(arr, animalName) and function remove(arr, animalName)
let newArr = [...arr]
Now, when I test this using the functions above. I will get one function that adds a new animal and the other function that removes an animal from the array all without mutation the original array.
function add(arr, animalName)
let addAnimal = add(animal, 'monkey')
console.log(addAnimal)
//output: ['lion', 'eagle', 'cheetah', 'bear', 'giraffe', 'monkey']
function remove(arr, animalName)
let removedAnimal = remove(animal, 'lion')
console.log(removedAnimal)
//output: ['eagle', 'cheetah', 'bear', 'giraffe']
When I run a console.log on the global variable animals from earlier. The global variable did not change at all.
let animals = ['lion', 'eagle', 'cheetah', 'bear', 'giraffe']
console.log(animals)
//output: ['lion', 'eagle', 'cheetah', 'bear', 'giraffe']
This is the benefit of using functional programming as a way to copy the global variable within the scope of the function. Then from there can mutate or change it without affecting the global variable and thus returning a new copy of the variable or object.
This content originally appeared on DEV Community and was authored by Christian Falucho
Christian Falucho | Sciencx (2021-06-22T23:25:14+00:00) Day 7 of #100DaysOfCode!. Retrieved from https://www.scien.cx/2021/06/22/day-7-of-100daysofcode/
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