can't sorting an array of objects code example

Example 1: sort array of objects by string property value

function compareFirstNames( a, b ) {
  if ( a.first_name < b.first_name ){
    return -1;
  }
  if ( a.first_name > b.first_name ){
    return 1;
  }
  return 0;
}

var people =[
    {"first_name":"Carol", "age":29},
    {"first_name":"Anna", "age":32},
    {"first_name":"Bob", "age":32}
];

people.sort( compareFirstNames ); //people is now sorted by first name from a-z

Example 2: sort array of objects javascript by value

let orders = [
  { 
    order: 'order 1', date: '2020/04/01_11:09:05'
  },
  { 
    order: 'order 2', date: '2020/04/01_10:29:35'
  },
  { 
    order: 'order 3', date: '2020/04/01_10:28:44'
  }
];


console.log(orders);

orders.sort(function(a, b){
  let dateA = a.date.toLowerCase();
  let dateB = b.date.toLowerCase();
  if (dateA < dateB) 
  {
    return -1;
  }    
  else if (dateA > dateB)
  {
    return 1;
  }   
  return 0;
});

console.log(orders);