What is the difference between the pipe and compose functions in JavaScript?

 

Question: What is the difference between the pipe and compose functions in JavaScript?

Answer: 

In JavaScript, both the pipe and compose functions are used to chain together multiple functions and pass the output of one function as the input to the next. However, they differ in the order in which the functions are executed.

The pipe function typically applies functions in a "left-to-right" or "bottom-up" order. That is, the functions are applied in the order they are passed to the pipe, with the output of each function being passed as the input to the next.

Here's an example of the pipe function :

const pipe = (...fns) => x => fns.reduce((v, f) => f(v), x);
const add = a => b => a + b;
const multiply = a => b => a * b;
const add10 = add(10);
const multiplyBy2 = multiply(2);
const result = pipe(add10,multiplyBy2)(2);
console.log(result) // 24

The add10 and multiplyBy2 functions are passed to the pipe function. Since the pipe function applies them left-to-right, the input of 2 is passed to add10 first and then passed to multiplyBy2 as input.

On the other hand, the compose function applies functions in a "right-to-left" or "top-down" order. That is, the functions are applied in the reverse order they are passed to the compose, with the output of the last function being passed as the input to the first.

Here's an example of the compose function :

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x);
const result = compose(multiplyBy2, add10)(2);
console.log(result) // 24

In this case, the multiplyBy2 and add10 functions are passed to the compose function. Since the compose function applies them right-to-left, the input of 2 is passed to multiplyBy2 first and then passed to add10 as input.

It is worth noting that both pipe and compose functions are similar in concept, the main difference is in the order of the function execution. The choice between pipe and compose depends on the use case and the developer's preference.

In general, Pipe is most useful when you want to pass the output of the first function to the next one, and compose is more useful when you want to pass the output of the last function to the first one, It all depends on the flow of data and the desired end result.