Right Click

Use the mousedown event type instead of click
yourThing.addEventListener(`mousedown`, clickThing)
Check the MouseEvent buttons property
function clickThing(event) {
  if (event.buttons == 1) { // check if the left mouse button is pressed
    // your left click code here
  else if (event.buttons == 2) { // check if the right mouse button is pressed
    // your right click code here
Disable the context menu with the contextmenu event type
yourThing.addEventListener(`contextmenu`, disableContextMenu)

function disableContextMenu(event) {
  // the default browser action is to show the context menu
  // this prevents the default browser action from happening