calc-task.js

const one = () => 1;
const two = () => 2;
const three = () => 3;

function op(fn) {
	return function() {
		return (vars) => Array.from(arguments)
    	.map(x => typeof x === 'function' ? x(vars) : +x).reduce(fn)
	};
}

const v = name => vars => vars[name];

const plus = op((x,y) => x + y);
const mult = op((x,y) => x * y);

const result = plus(one(), 10, v('foo'), mult(two(), three(), 5));
console.log(result({ foo:1 })); // 42