JavaScript dynamically adds HTML nodes

I've never had much contact with the project that needs to add and delete HTML nodes dynamically, this project is used and learned.

Add a <tr id= "tr" > Label,<tr> tag with 4 <td> tags in a <table id= tab > tab

function inserttr () {   = document.createelement ("tr");    = "<td></td>" + "<td></td>" + "<td></td>" + "<td></td>";    = "tr";    = html;   document.getElementById ("tab"). appendchild (tr);}   

Here is the <tr> tag inside the 4 <td> tag HTML code as a string to write this <tr> tag

Remove a <tr id= "tr" > Label from a <table id= tab > tab

function deltr () {  document.getElementById("tab"). RemoveChild (document.getElementById ("tr"));}

JavaScript dynamically adds HTML nodes