logDecorator makes decorated function that logs to the console function name, arguments and result.

logDecorator.js

sub(mult(2, 5), add(2, div(12, 3))) // 4

function sub(x, y){
   return x - y
}

function mult(x, y){
    return x * y
}

function div(x, y){
    return x / y
}

function add(x, y){
    return x + y
}

let operations = [sub, mult, div, add]

function logDecorator(fn){
    return function decor(...args){
        const result = fn(...args)
        console.log(`${fn.name}(${args.join(', ')}) -> ${result}`)
        return result
    }
}

[sub, mult, div, add] = operations.map(logDecorator)

sub(mult(2, 5), add(2, div(12, 3))) 
//  mult(2, 5) -> 10
//  div(12, 3) -> 4
//  add(2, 4) -> 6
//  sub(10, 6) -> 4
// 4