Javascript Check if a Date is contained in an Array - React Js

<!DOCTYPE html>
<html>
  <head>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  </head>

<body>
    <div id="app">
      <h2>Vue js check date existence</h2>
      <input type="date" v-model="inputDate" />
      <button @click="checkDate">Check Date</button>
    </div>

if (this.isDateContained) {
              alert("The date is contained in the array.");
            } else {
              alert("The date is not contained in the array.");
            }
          },
          areDatesEqual(date1, date2) {
            return (
              date1.getFullYear() === date2.getFullYear() &&
              date1.getMonth() === date2.getMonth() &&
              date1.getDate() === date2.getDate()
            );
          },
        },
      });
    </script>