CODE EXAMPLE FOR TYPESCRIPT

array of objects how to check if property has duplicate

var yourArray = [

{Index: 1, Name: "Farley, Charley", EmployeeCode: "12", PaymentType: "Void", CheckDate: "01/04/2012"},
{Index: 2, Name: "Farley, Charley", EmployeeCode: "12", PaymentType: "Void", CheckDate: "01/04/2012"},
{Index: 3, Name: "Tarley, Charley", EmployeeCode: "12", PaymentType: "Void", CheckDate: "01/04/2012"}
];

   unique = [...new Set(yourArray.map(propYoureChecking => propYoureChecking.Name))];
if (unique.length === 1) {
console.log(unique);
}