pickBy-focus.js

const { pickBy } = require('ramda');

const obj = {
  a: 1,
  b: 2,
  A: 3,
  B: 4
};

// ---

const keyIsUpperCase = (val, key) =>
  key.toUpperCase() === key;

pickBy(keyIsUpperCase, obj);

// ---

const focus = (idx, fn) =>
  (...args) => fn(args[idx]);

const isUpperCase = (str) =>
  str.toUpperCase() === str;

const keyIsUpperCase_ = focus(1, isUpperCase);

pickBy(focus(1, isUpperCase), obj); // { A: 3, B: 4 }
pickBy(keyIsUpperCase_, obj);       // { A: 3, B: 4 }