count array length into variable javascript code example

Example 1: array length javascript

var arr = [10,20,30,40,50]; //An Array is defined with 5 instances

var len= arr.length;  //Now arr.length returns 5.Basically, len=5.
console.log(len); //gives 5
console.log(arr.length); //also gives 5

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)