How can you select an HTML table row using JavaScript and then insert new data into it?

In JavaScript, you can select an HTML table row using the getElementsByTagName method to get all the <tr> elements in the table, then use the item method or the [] operator to select a specific row. Once you have selected the row, you can use the insertCell method to add new cells to the row and the innerHTML property to insert data into the cells.

Here's an example of how you can select the first row of an HTML table with the id "myTable" and insert new data into it:

// Get the table 
var table = document.getElementById("myTable"); 
 
// Get the first row of the table 
var row = table.getElementsByTagName("tr")[0]; 
 
// Insert a new cell at the end of the row 
var newCell = row.insertCell(-1); 
 
// Insert some data into the new cell 
newCell.innerHTML = "New Data"; 

You can also use the querySelector method to select the table and the row

let table = document.querySelector("#myTable") 
let row = table.querySelector("tr:first-child") 

In this example, the first line selects the table element with the id "myTable". The second line selects the first row of the table by getting all the <tr> elements in the table and selecting the first one using the [0] operator. The third line inserts a new cell at the end of the row using the insertCell method, passing -1 as an argument. Finally, the fourth line sets the innerHTML property of the new cell to "New Data".

You can also use the createElement method to create a new element, and the appendChild method to insert it into the table.

let newRow = document.createElement("tr") 
let newData = document.createElement("td")  
newData.innerHTML = "New Data" newRow.appendChild(newData) table.appendChild(newRow) 

In this example, a new `<tr>` element is created using the `createElement` method, and then a new `<td>` element is created and its innerHTML is set to "New Data". The new `<td>` element is then appended to the new `<tr>` element, and the new `<tr>` element is then appended to the table using the `appendChild` method.

It's important to note that these examples just cover the basics of inserting new data into an HTML table row using JavaScript. There are many other ways to do this, and you should choose the approach that best fits your needs.