i am not able to get input data in html table cells to JavaScript variables

I have tried to get input from user in the cells of table created using html to get that data into variable of JavaScript .

I was trying to get data from rows cell of table to JavaScript variables one by one but getting undefined in place of data when alerting the data after summit.

please help me with this I want to get the data from these table CELLS and alert data using java script in final by saving the data typed by user in cells to JavaScript variable variables.

HTML code

 <table border = "2" cellpadding = "6" cellspacing = "6" bordercolor = "white" bgcolor = "red" class="center" id="mytable" >
        <tr>
            <th style="background: white;">EDUCATION</th>
            <th style="background: white;">INSTITUTE</th>
            <th style="background: white;">PERCENTAGE</th>
        </tr>
        <tr>
            <td style="color: white;">10 th</td>
            <td id="10inst"><input type="text"></td>
            <td  id="10per"><input type="text"></td>
        </tr>
        <tr>
            <td style="color: white;" >12 th</td>
            <td  id="12inst"><input type="text"></td>
            <td  id="12per"><input type="text"></td>
        </tr>
        <tr>
            <td style="color: white;">Graduaction</td>
            <td  id="gradinst"><input type="text"></td>
            <td  id="gradper"><input type="text"></td>           
        </tr>
        <tr>
            <td style="color: white;">Masters</td>
            <td id="masterinst"><input type="text"></td>
            <td id="masterper"><input type="text"></td>           
        </tr>

    </table><br><br>

JavaScript code

var inst10 = document.getElementById("mytable").value;
var inst12 = document.getElementById("12inst").value;
var masterinst = document.getElementById("masterinst").value;
var per10 = document.getElementById("10per").value;
var per12 = document.getElementById("12per").value;
var masterper = document.getElementById("masterper").value;
var gradinst=document.getElementById("gradinst").value;
var gradper=document.getElementById("gradper").value;