Javascript helper functions

helpers.js

const isLowerCase = str => str === str.toLowerCase();

const isNullOrUndefined = val => val === undefined || val === null;

const smoothScroll = element =>
  document.querySelector(element).scrollIntoView({
    behavior: 'smooth'
  });

const splitLines = str => str.split(/\r?\n/);

// Arrays:
const matchingElements = (array1, array2) => 
  array1.filter(element => array2.includes(element));

const arrayDiff = (array1, array2) => {
  const setArray = new Set(array2);
  return array1.filter(arr => !setArray.has(arr));
};

const removeDuplicates = arr => [...new Set(arr)];