[HELP]Javascript

How can i get the value of the username and password with javascript and display it with alert command?


alert("username:"+username+" password:"+password);


<div id="sTable">
    <table>
        <tr>
            <th>User ID</th><th>Username</th><th>Password</th><th>Type</th><th>Employee ID</th><th colspan=2>Action</th>
        </tr>
        <tr>
            <span id="resultId0"><td>0</td><td>george</td><td>1234</td><td>admin</td><td>0</td></span>
        </tr>
        <tr>
            <span id="resultId26"><td>26</td><td>janet</td><td>1234</td><td>employee</td><td>1</td></span>
        </tr>
        <tr>
            <span id="resultId27"><td>27</td><td>ronald</td><td>1234</td><td>employee</td><td>4</td></span
        </tr>
    </table>
</div>