object - javascript dom conflict: how to start at column 2 -

my javascript dom model conflicting. have exporttable on 1 side generate indexnumber , on other side imports data (firsname, lastname , points importform. try indexnumber on column 1, firstname in 2, lastname in 3 , points in 4.

at moment indexnumber in column 1(good) firstname starts in column 1 (not good). if adding (see script) newrow.insertcell(1); console protests.

who can me?

<script>     var button3 = document.getelementbyid("button2");         button3.onclick= adddata;          function adddata() {             // collect data firstname, lastname, points              var firstname = document.getelementbyid("firstname");             var lastname = document.getelementbyid("lastname");             var points = document.getelementbyid("points");              var exporttable = document.getelementbyid("exporttable");             var newrow = exporttable.insertrow(-1);             var cel1 = newrow.insertcell(0); //i can not start here insertcell(0);              var cel2 = newrow.insertcell(1);             var cel3 = newrow.insertcell(2);              cel1.innerhtml = firstname.value;             cel2.innerhtml = lastname.value;             cel3.innerhtml = points.value;               //instal number             var amountrows = exporttable.rows.length;              (var = 1; < amountrows; i++) {                 exporttable.rows[i].children[0].innerhtml = i;             }         }  </script>