One Solution is leveraging JS Set to find out unique category and use it to get the count.

const data = [
  { name: 'Apple', category: 'fruit' },
  { name: 'Orange', category: 'fruit' },
  { name: 'Banana', category: 'fruit' },
  { name: 'Milk', category: 'drink' },
  { name: 'Juice', category: 'drink' },
];

const categories = new Set();

data.forEach((item) => {
    categories.add(item.category);
})

const result = [];
categories.forEach((category) => {
    const val = data.filter((item) => item.category === category);
  
  result.push({count: val.length, category})
})

console.log(result);

I don't know if this is the right way to do but it should work

const data = [
  { name: 'Apple', category: 'fruit' },
  { name: 'Orange', category: 'fruit' },
  { name: 'Banana', category: 'fruit' },
  { name: 'Milk', category: 'drink' },
  { name: 'Juice', category: 'drink' },
];

function filterArray(arr) {
    const map = new Map()
    arr.map(i => map.set(i.category, map.get(i.category) + 1 || 1))
    return [...map].map(i => ({'count': i[1],'category': i[0]}))
}

let result = filterArray(data)
console.log(result)