Insert th in thead

Question

I want to insert a th tag inside tr of thead element of a table. I am using insertCell method of row object created under

Answer 1

You can also use the insertCell method as originally requested. You just have to change the outerHTML to overwrite the <td> created by the insertCell method:

var table = document.createElement("TABLE")
var row   = table.insertRow(0);
    row.insertCell(0).outerHTML = "<th>First</th>";  // rather than innerHTML

To match the example given:

HTML

<table id="table">
  <thead>
    <tr>
      <th>First</th>
    </tr>
  <thead>
</table>

Javascript

var tr = document.getElementById('table').tHead.children[0];
    tr.insertCell(1).outerHTML = "<th>Second</th>"  // some browsers require the index parm -- 1

Answer 2

You can add this functionality to the native HTMLTableRowElement by changing it's prototype:

HTMLTableRowElement.prototype.insertCell = (function(oldInsertCell) {
    return function(index) {
        if (this.parentElement.tagName.toUpperCase() == "THEAD") {
            if (index < -1 || index > this.cells.length) {
                // This case is suppose to throw a DOMException, but we can't construct one
                // Just let the real function do it.
            } else {
                let th = document.createElement("TH");
                if (arguments.length == 0 || index == -1 || index == this.cells.length) {
                    return this.appendChild(th);
                } else {
                    return this.insertBefore(th, this.children[index]);
                }
            }
        }
        return oldInsertCell.apply(this, arguments);
    }
})(HTMLTableRowElement.prototype.insertCell);

After this code is run, any new HTMLTableRowElements ("td" tags) will check to see if the parent is a thead tag. If so, it will do the same functionality as insertCell, but using a th tag instead. If not, it will just use the original insertCell functionality.

document.querySelector("thead > tr").insertCell(); // inserts a th into a tr inside a thead
document.querySelector(":not(thead) > tr").insertCell(); // inserts a td into a tr not inside a thead

Note that it is generally not recommended to extend the native objects.

Answer 3

You can do it with vanilla JavaScript. Try this:

HTML

<table id="table">
  <thead>
    <tr>
      <th>First</th>
    </tr>
  <thead>
</table>

JavaScript

var tr = document.getElementById('table').tHead.children[0],
    th = document.createElement('th');
th.innerHTML = "Second";
tr.appendChild(th);

Here is an example http://codepen.io/anon/pen/Bgwuf

Answer 4

Use table.tHead.children[0].appendChild(document.createElement("th")) method instead. Basically you have to create a th at runtime and insert it into your thead.