JavaScript saves and calculates the number type variables in the page

Previously, the html page was embedded with the following javascript fragment, but the i value is increased by 1 when 1 button is clicked, but the initial value of i remains unchanged after two clicks.

<script language=javascript>

      var i=2;

</script>

The variable is then declared in an test object as follows. This allows the value of test. i to be saved every time test. i is changed

<script language=javascript>

      var test={};

      test.i=2;

</script>