connecting multiple static html pages to a single js file

I am trying to recreate the halo 3 UI with vanilla js, html, and css as my first solo adventure into front end web dev. Currently, I have the main menu and links to other html files. I have a single js file to handle event listeners and whatnot. I am running into an issue where i am getting a NULL reference error when trying to access elements on another page. This makes sense to me as those elements have not been rendered but the NULL error is not allowing the event listeners for the current page to work. code bellow:

/** main menu vars */
const trailer_btn = document.getElementById('show-trailer-btn');
const trailer = document.getElementById('trailer');
const trailer_escape_btn = document.getElementById('trailer-escape-btn');

/** theater menu vars */
const film_list_btn = document.getElementById('change-film-btn');
const film_list = document.getElementById('film-menu');




let trailer_playing = false;
let film_list_visible = false;



/**    MAIN MENU     */

/** event listener for trailer */
trailer_btn.addEventListener('click', ()=>{
    trailer.style.visibility='visible';
    trailer_escape_btn.style.visibility='visible';
    trailer_playing = true;
    trailer.play();
})

/**event listener to stop trailer */
trailer_escape_btn.addEventListener('click',()=>{
    trailer_playing = false;
    trailer.pause();
    trailer.currentTime = 0;
    trailer.style.visibility='hidden';
    trailer_escape_btn.style.visibility='hidden';
})


/**     THEATER PAGE     */

film_list_btn.addEventListener('click', ()=>{
    console.log('click')
    film_list.style.visibility = 'visible'
})

if i were to comment out the main menu event listeners, then the theater page event listeners will work.

so to summarize i want a single js file that will be able to handle the interactivity for all the static html pages.

I’ve commented out the main menu event listeners and because those elements are not on the theater page, it will work but if i leave them uncommented, i get a null reference error because the elements from the main menu are not rendered.