maxdepth.js

// use transducers
const appendTo = flip(append);

const apCh = (fn, accVal) => (item) => accVal = fn(accVal, item);

const steps = [
  filter(test(/[()]/)),
  map((item) => item === '(' ? 1 : -1),
  map(apCh(add, 0)), // scan transducer
];

const transformer = compose(...steps);

const maxdepth = compose(
  apply(Math.max),
  transduce(transformer, appendTo, []),
  split('')
);


const s = `(5*(2+(6-3)-(2-(1))))`;

maxdepth(s);