trilium/src/public/javascripts/services/context_menu.js

const $contextMenuContainer = $("#context-menu-container");

function initContextMenu(event, contextMenuItems, selectContextMenuItem) {
    event.stopPropagation();

    $contextMenuContainer.empty();

    function addItems($parent, items) {
        for (const item of items) {
            if (item.title === '----') {
                $parent.append($("<div>").addClass("dropdown-divider"));
            } else {
                const $icon = $("<span>");

                if (item.uiIcon) {
                    $icon.addClass("jam jam-" + item.uiIcon);
                } else {
                    $icon.append("&nbsp;");
                }

                const $item = $("<li>")
                    .addClass("dropdown-item");

                const $link = $("<a>")
                    .append($icon)
                    .append(" &nbsp; ") // some space between icon and text
                    .prop("data-cmd", item.cmd)
                    .append(item.title);

                $item.append($link);

                if (item.enabled !== undefined && !item.enabled) {
                    $link.addClass("disabled");
                }

                $link.click(async function (e) {
                    const cmd = $(e.target).prop("data-cmd");

                    e.originalTarget = event.target;

                    await selectContextMenuItem(e, cmd);
                });

                if (item.items) {
                    $item.addClass("dropdown-submenu");
                    $link.addClass("dropdown-toggle");

                    const $subMenu = $("<ul>").addClass("dropdown-menu");

                    addItems($subMenu, item.items);

                    $item.append($subMenu);
                }

                $parent.append($item);
            }
        }
    }

    addItems($contextMenuContainer, contextMenuItems);

    // code below tries to detect when dropdown would overflow from page
    // in such case we'll position it above click coordinates so it will fit into client
    const clickPosition = event.pageY;
    const clientHeight = document.documentElement.clientHeight;
    const contextMenuHeight = $contextMenuContainer.height();

    let top;

    if (clickPosition + contextMenuHeight > clientHeight) {
        top = clientHeight - contextMenuHeight - 10;
    } else {
        top = event.pageY - 10;
    }

    $contextMenuContainer.css({
        display: "block",
        top: top,
        left: event.pageX - 20
    }).addClass("show");
}

$(document).click(() => $contextMenuContainer.hide());

export default {
    initContextMenu
}