Chartjs-How to reorganize data to display how many times a string appears in an array object?

First you filter it by each category, then make an array of language Strings. Then make object that holds each language appearance by counting it.

const categroy1data = data.filter(val => val.category === 1).map(val => val.language);
// => ['Danish', 'Dutch', 'Spanish' ... ]

const category1result = {}
category1data.forEach(val => {
  category1result[val] = 1 + (category1result[val] || 0)
})
// { 
//   Danish: 3,
//   Dutch: 2,
//   Spanih: 1,
// }