const FRUITS = ["banana", "apple", "orange", "banana", "orange", "apple", "apple", "orange", "orange", "banana", "orange", "banana"]

const total = FRUITS.reduce((map, fruit) => ({

  ...map,

  [fruit]: (map[fruit] || 0) + 1,

}), {})

console.log(total) // { banana: 4, apple: 3, orange: 5}

const posts = [

    {id: 1, category: "frontend", title: "All About That Sass"},

    {id: 2, category: "backend", title: "Beam me up, Scotty: Apache Beam tips"},

    {id: 3, category: "frontend", title: "Sanitizing HTML: Going antibactirial on XSS attacks"}

];

​

const categoryPosts = posts.reduce((acc, post) => {

    let {id, category} = post;

    return {...acc, [category]: [...(acc[category] || []), id]};

}, {});