What can I do to detect when a down arrow is pressed while a text box is being focused on?

edit

One way to detect when a down arrow is pressed while a text box is being focused on is to add an event listener for the "keydown" event on the input element. Then, in the event listener function, check if the key pressed was the down arrow key using the event.keyCode property (or event.key if supported by the browser).

const input = document.querySelector("#myInput");

input.addEventListener("keydown", function(event) {
  if (event.keyCode === 40 || event.key === "ArrowDown") {
    console.log("Down arrow key pressed!");
    // do something here
  }
});

<input id="myInput"/>

Note that the keyCode property is deprecated and may not work in all browsers. It is recommended to use the key property instead, which returns the actual physical key that was pressed.