title: Uncaught ReferenceError: txtMaking_F is not defined
body: <p>I use two textbox to sum number but showing error..</p>
  
  <pre><code>    &lt;script&gt;
          function getPrice(tMaking, tHandeling, tTotal) {
              var obj_tMaking = document.getElementById(txtMaking_F)
              var obj_tHandeling = document.getElementById(txtHandeling_F)
              var obj_tTotal = document.getElementById(txtTotal_F)
              if (obj_tMaking.value != "" &amp;&amp; obj_tHandeling.value != "") {
                  obj_tTotal.value = parseInt(obj_tMaking.value) + parseInt(obj_tHandeling.value);
              }
              else {
                  obj_tTotal.value = "";
              }
          }
      &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;input name="grdView$ctl08$txtMaking_F" type="text" id="grdView_ctl08_txtMaking_F" class="classMaking" onchange="javascript:return getPrice('grdView_ctl08_txtMaking_F','grdView_ctl08_txtHandeling_F','grdView_ctl08_txtTotal_F');" style="width: 60px;" /&gt;
      &lt;input name="grdView$ctl08$txtHandeling_F" type="text" id="grdView_ctl08_txtHandeling_F" class="classHandling" onchange="javascript:return getPrice('grdView_ctl08_txtMaking_F','grdView_ctl08_txtHandeling_F','grdView_ctl08_txtTotal_F');" style="width: 60px;" /&gt;
      &lt;input name="grdView$ctl08$txtTotal_F" type="text" id="grdView_ctl08_txtTotal_F" class="classTotal" style="width: 100px;" /&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/TcM5J.jpg" alt="enter image description here"></p>