One can argue that is not an impure function by design but think about it-it’s not possible to do anything with it except mutating non-local data or doing side effects. On the other hand,, are impure functions. JavaScript already has some functions that enable functional programming. When we satisfy these conditions, we can say our code is functional. Use pure functions: fixed output for fixed inputs, and no side effects.So far, we have learned that functional programming is dependent on a few rules. It’s impossible to parallelize or memoize them. Have a look at the previous two functions. What’s the current value of id_count? Which other functions are modifying id_count? Are there other functions relying on id_count?īecause of these reasons, we only use pure functions in functional programming.Īnother benefit of pure functions is that they can be parallelized and memoized. This can be troublesome if we had to debug this code. ![]() This is also an impure function, and that too for a couple of reasons-(1) it uses a non-local variable for computing its output, and (2) it creates a side effect in the outside world by modifying a variable in that world. If SECRET were to change, the getId function will return a different value for the same input. ![]() The reason being that it uses the global variable SECRET for computing the output. This is because, for a fixed value of a and b, the output will always be the same. Also, they cause no side effects in the outside world. Pure functions take some input and give a fixed output. In the end, we will explore different concepts associated with functional programming and see why they are so powerful.īefore getting into functional programming, though, one needs to understand the difference between pure and impure functions. We will also explore various JavaScript methods and features that make it possible. In this article, we will talk about doing functional programming using JavaScript. Also, functional programming requires us to write pure, deterministic functions which are less likely to be buggy. This is achieved by avoiding using flow-control statements ( for, while, break, continue, goto) which make the code harder to follow. Functional programming is a paradigm of building computer programs using expressions and functions without mutating state and data.īy respecting these restrictions, functional programming aims to write code that is clearer to understand and more bug resistant.
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