Semantic Editor Combinators in javascript

semantic_editor.js

// see http://conal.net/blog/posts/semantic-editor-combinators

const o = (...f) => {
  if(f.length === 0) {
    return x => x;
  } else {
    return x => f[0](o(...f.slice(1))(x));
  }
};


const get = i => f => o => {
	const op = Object.assign({},o);
	op[i] = f(op[i]);
	return op;
};

const index = i => f => a => {
	const ap = a.slice();
	ap[i] = f(ap[i]);
	return ap;
};

const map = f => a => a.map(x => f(x));

const result = f => g => x => f(g(x));

const argument = g => f => x => f(g(x));

const example = o(index(0), get("x"), map)(x => +x) ( [{ x : ["1","2"], y : 3},3] );
console.log(example);