JavaScript has a built-in calculator, and mathematical operations can be done directly in the console. To add 2 numbers in Javascript, get the values from the fields and parse them into integers before adding: var first = document.getElementById ("FIRST").value; var second = document.getElementById ("SECOND").value; var added = parseInt (first) + parseInt (second); That covers the basics, but let us walk through a few more examples in this guide. When you include JavaScript in your HTML document with the