function diff(oldList, newList) {

const remove = [];

const add = [];

oldList.forEach((item) => newList.indexOf(item) === -1 && remove.push(item));

newList.forEach((item) => oldList.indexOf(item) === -1 && add.push(item));

return { add, remove };

}

function unique(arr) {

if (arr.length === 0) {

return arr;

}

const isObjArray = arr[0] instanceof Object;

arr = isObjArray ? arr.map((e) => JSON.stringify(e)) : arr;

const unique = arr.filter((e, pos) => arr.indexOf(e) === pos);

return isObjArray ? unique.map((e) => JSON.parse(e)) : unique;

}

function flatten(arr) {

return [].concat.apply([], arr);

}

function getCaseInsensitiveStringSorter() {

return (a, b) => {

const strA = a.toLowerCase();

const strB = b.toLowerCase();

if (strA < strB) {

return -1;

}

if (strA > strB) {

return 1;

}

return 0;

};

}

module.exports = {

diff,

unique,

flatten,

getCaseInsensitiveStringSorter,

};