JSFiddle - React, Tailwind, and code Playground

HTML

<html>
  <body>
    <input
      id="start_date"
      type="date"
      class="form-control"
      data-model="startDate"
    />
    <input
      id="end_date"
      type="date"
      class="form-control"
      data-model="endDate"
    />
    <button onclick="showVal()">Show</button>
  </body>
  <script>
    function showVal() {
      alert(compute());
    }

    function compute() {
      var start_date_arr = document
        .getElementById("start_date")
        .value.split("-");
      var end_date_arr = document.getElementById("end_date").value.split("-");
      var start_date = start_date_arr.pop();
      var end_date = end_date_arr.pop();
      if (JSON.stringify(start_date_arr) !== JSON.stringify(end_date_arr))
        return false;
      else return end_date - start_date == 1;
    }
  </script>
</html>