find2.js

import {
  compose,
  findIndex,
  cond,
} from 'lodash/fp';

const MY_LIST = [/* items here */];

const findMyItemIndex = findIndex(item => item === 'MY_ITEM');
const changeItemToSomething = () => // returns NEW object (immutable)

const doMagic = (item, list) => {
  const index = findMyItemIndex(item);
  
  return index > -1
    && changeItemToSomething(item, list)
    || list;
};

doMagic({a: 1}, MY_LIST);