test.js

const tasks = [
  {
    description: 'Test',
    completed: false
  },
  {
    description: 'Test2',
    completed: true
  }
];
const activeTasks = tasks.filter((item) => {
  console.log('Внутри коллбека филтер');
  console.log(item);
  return item.completed == false;
});

console.log('Все активные задачи:');
console.log(activeTasks);