typescript count array condition

let data = [ { "id": 1, "is_read": true, }, { "id": 2, "is_read": true, }, { "id": 3, "is_read": false, }, { "id": 4, "is_read": true, }, ],
length = data.filter(function(item){
  return item.is_read;
}).length;
console.log(length)

var words = ['Hello', 'world'];

var lengths = words.map(function(word) {
  return word + ' = ' + word.length;
});

console.log(lengths);

var lengths = chars.map(function(word){
 return word.length
})