Once disable arrow key scrolling in users browser, how to enable it

Question

Disable arrow key scrolling in users browser Zeta was given correct answer for how to disable the arrow keys.

I need to re-enable arrow key navigation once its disabled.

$('main navigation').has('drop down').bind('keyup', function (e) {
    if (e.keyCode == 40) {hover(e,$(this));} //Down Arrow Key press, how mega menu
    if (e.keyCode == 38) {unhover(e);} //Up Arrow Key Press, hide mega menu
    if (e.keyCode == 9) {checkTab();} //check if tab pressed
}

var checkTab = function (){
        // i check, if tab focus to the main menu anchor
    if($('main navigation').is(':focus')){
        var keys = [];
        window.addEventListener("keydown",
            function(e){
                keys[e.keyCode] = true;
                switch(e.keyCode){
                    case 37: case 39: case 38:  case 40: // Arrow keys
                    case 32: e.preventDefault(); break; // Space
                    default: break; // do not block other keys
                }
            },
        false);
        window.addEventListener('keyup',
            function(e){
                keys[e.keyCode] = false;
            },
        false);             
        console.log('focused')
    }
    else {
        console.log('f out')    
    }                   
}

this works fine, but as I have bind window.event to disable. once disabled I cant enable. Need help in this point.

Answer 1

Use another variable to determine whether you should currently block the arrow keys:

var useArrowKeysToScroll = false;

/* ... */
function(e){
    keys[e.keyCode] = true;
    if(!useArrowKeysToScroll && 
           ((e.keyCode >= 37 && e.keyCode <= 40) || 
             e.keyCode == 32)){
        e.preventDefault();
    }
    /* handle other keys etc... */
}, /* ... */

If useArrowKeysToScroll is false it the arrow keys and space bars won't result in scrolling.