{"id":6582,"date":"2019-12-19T19:00:33","date_gmt":"2019-12-19T19:00:33","guid":{"rendered":"https:\/\/cheesecakelabs.com\/blog\/?p=6582\/"},"modified":"2022-07-01T17:09:28","modified_gmt":"2022-07-01T17:09:28","slug":"functional-programming-game-js","status":"publish","type":"post","link":"https:\/\/cheesecakelabs.com\/blog\/functional-programming-game-js\/","title":{"rendered":"Using functional programming to create a game in JS"},"content":{"rendered":"

There has been a lot of hype around the functional programming paradigm for some time and there are a lot of great books and articles about it on the internet, but it’s not so easy to find real examples with its application. So have I decided to create a game trying to follow its concepts using Javascript, <\/span>which is the most popular programming language today<\/span><\/a>. In this post, I will share some of this experience and tell you if it was worth it.<\/span><\/p>\n

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What is functional programming?<\/b><\/h2>\n

To keep it short, functional programming (FP) is a paradigm that attempts to reproduce the concept of mathematical functions, which is a relationship between the sets of domains (valid inputs) and the codomain (valid outputs). Mathematical function outputs are always related to just one input, so whenever a mathematical function is calculated with the same input, it returns the same output. This is one of FP\u2019s most important concepts, also known as <\/span>determinism<\/b>.<\/span><\/p>\n

Non-deterministic function example<\/strong>:<\/span><\/p>\n

let x = 1<\/span>\n\nconst nonDeterministicAdd = y => x + y<\/span>\n\nnonDeterministicAdd(2) \/\/ 3<\/span>\n\nx = 2<\/span>\n\nnonDeterministicAdd(2) \/\/ 4\n\n<\/span><\/pre>\n
Deterministic function example<\/strong>:<\/span><\/p>\n
const deterministicAdd = (x, y) => x + y<\/span>\n\ndeterministicAdd(1, 2) \/\/ 3\n\n<\/span><\/pre>\n
In addition to determinism, functions in FP seek not to cause changes beyond their scope. These types of functions are called <\/span>pure<\/span><\/a>. Last but not least, the data in FP must be immutable, meaning it cannot have its value changed after creation. These concepts together make testing, caching, and parallelism easier.<\/span><\/p>\n
Beside these basic concepts, I also tried to use Point-free style during the development of the game, which aims to make the code cleaner as it omits the use of unnecessary parameters and arguments. Here<\/span>\u00b9<\/span><\/a>\u00b2<\/span><\/a> are a couple of good references about it.  <\/span><\/p>\n
Since the beginning of the project, the intention was to create a game that runs in the browser. Because Javascript (JS) is a language that I feel comfortable with and is a multi-paradigm language, it was language I chose for this project.<\/span><\/p>\n
There are two excellent books about FP that I recommend:<\/span><\/p>\n