calculate two number and diplay next field without reload the page javascript

1var text1 = document.getElementById("Text1");
2var text2 = document.getElementById("Text2");
3
4function add_number() {
5   var first_number = parseFloat(text1.value);
6   if (isNaN(first_number)) first_number = 0;
7   var second_number = parseFloat(text2.value);
8   if (isNaN(second_number)) second_number = 0;
9   var result = first_number + second_number;
10   document.getElementById("txtresult").value = result;
11}

1<p>Enter First Number :</p>
2<br>
3<input type="text" id="Text1" name="TextBox1" oninput="add_number()">
4<br> <p>Enter Second Number :</p>
5<br>
6<input type="text" id="Text2" name="TextBox2" oninput="add_number()">
7<br>Result :
8<br>
9<input type="text" id="txtresult" name="TextBox3">