HELP!

home.js

var optionMenuOpen = false;
var optionMenuIndex = 0;

document.addEventListener("DOMContentLoaded", () => {
});

function backHandler() {
    if(optionMenuOpen) {
        document.getElementById("optionMenu-blur").style.display = "none";
        document.getElementById("optionMenu").style.display = "none";
        navigator.mozL10n.setAttributes(document.getElementById("softkey-left"), 
                                        'home-softkey-history');
        navigator.mozL10n.setAttributes(document.getElementById("softkey-center"), 
                                        'home-softkey-track');
        navigator.mozL10n.setAttributes(document.getElementById("softkey-right"), 
                                        'home-softkey-options');
        optionMenuOpen = false;
        optionMenuIndex = 0;
        document.removeEventListener('keydown', navOptionMenu);
        document.addEventListener('keydown', navDocument);
    } else {
        window.close();
    }
}

function navDocument(e) {
    switch(e.key) {
        case 'SoftLeft':
            break;
        case 'SoftRight':
            if(!optionMenuOpen) {
                document.getElementById("optionMenu-blur").style.display = "inline";
                document.getElementById("optionMenu").style.display = "inline";
                document.getElementById("softkey-left").textContent = "";
                navigator.mozL10n.setAttributes(document.getElementById("softkey-center"), 
                                                'global-softkey-select');
                document.getElementById("softkey-right").textContent = "";
                document.getElementById("option-0").focus();
                document.removeEventListener('keydown', navDocument);
                document.addEventListener('keydown', navOptionMenu);
                optionMenuOpen = true;
            }
            break;
        case 'Backspace':
            e.preventDefault();
            backHandler();
    }
}

function navOptionMenu(e) {
    if(optionMenuOpen) {
        for(i = 0; i < 4; i++) {
            document.getElementById("option-"+i).blur();
        }
        switch(e.key) {
            case 'Up':
                if (optionMenuIndex < 0) {
                    optionMenuIndex = 3
                }
                document.getElementById("option-"+optionMenuIndex).focus();
                break;
            case 'Down':
                if (optionMenuIndex > 3) {
                    optionMenuIndex = 0
                }
                document.getElementById("option-"+optionMenuIndex).focus();
                break;
            case 'Backspace':
                e.preventDefault();
                backHandler();
                break;
        }
    } else {
        console.log("Option menu not open!")
    }
}

document.addEventListener("keydown", navDocument);