get number of items in a list js code example

Example 1: use .map to count length of each element in an array

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

Example 2: 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)