add.js

function add(...args) {
	const sum = args.reduce((prev, curr) => prev + curr, 0);
	const ret = add.bind(void 0, sum);
	ret.value = ret.valueOf = () => sum;
	ret.add = ret;
	return ret;
}

console.log(add(1, 2).value() === 3);
console.log(add(1, 2)(3).value() === 6);
console.log(+add(2, 3, 4)(5)(4, 6) === 24);
console.log(add(2, 3, 4)(5).add(4,6) + 5 === 29);