Are you programming in JavaScript or a combination of HTML/CSS and JavaScript?
Have you looked in the JavaScript documentation online (such as the MDN link given in KA's JavaScript Documentation tab) to see if JavaScript has a way to access the scroll wheel movement?  

My answer courtesy of X who cannot comment here:

There is indeed a mouseScrolled function in Processing.js. However as shown here: https://www.khanacademy.org/computer-programming/i/3452477363 it may still scroll your whole browser. In the comments at the top of that program there is a link to a GitHub issue that details a "monkey patch" type fix, however Khan's guardians might not take to kindly to it's use. A better solution would be to use the scroll event directly: https://developer.mozilla.org/en-US/docs/Web/API/WheelEvent. Unfortunately you'd still have to break rules to use this in a Processing.js scratchpad. My only suggestion for a close to perfect fix is to move to an HTML scratchpad. Hope this helps! 

Hi everyone,

Lots of thanks to HM Wogglebug TE for giving a solution for this on my project. He showed me how to create my own event listener for scrolling. The problem with mouseScrolled() is that it would still scroll the khan academy page along making the canvas and the code scroll out of the screen. The code which Wogglebug showed me to create the event listener is written below for anyone in the future, just insert this segment into your draw = function () {} and will detect if the user is scrolling up or down using numbers.

Thanks you guys so much - Aarav

var externals, cnv = externals.canvas;

cnv.onwheel = function (e) {
e.preventDefault();

println(e.wheelDelta);
};