Functional Programming

Function composition

Curry functions

var add = function (a){
    return function(b){
        return a + b;
    }
}
// console.log(add(a,b)); <- incorrect call
// calling one function at a time
var func_add_2 = add(1); // return a function which adds 1 to the argument
var final_output = func_add_2(5);
console.log(final_output);
// more direct approach
final_output = add(1)(5); // curry function call
console.log(final_output);

compose function

Spread syntax (...)

using reduceRight

// function composition of any number of functions
const compose = (...fns) => x => fns.reduceRight((y, f) => f(y), x); 
const double = x => x * 2
const square = x => x * x

// function composition
var output_final = compose(square, double)(2);
console.log(output_final);

Using pipe function

// function composition using pipe of any number of functions
const pipe = (...fns) => x => fns.reduce((y, f) => f(y), x); 
const double = x => x * 2
const square = x => x * x

// function pipe
var output_final = pipe(square, double)(2);
console.log(output_final);

Libraries

• Ramda: compose and pipe
• Lodash: flowRight (compose) and flow (pipe)

Recursion

trampoline or tail-call techniques to avoid stack error.