keyboard events - Detecting arrow key presses in JavaScript - Stack Overflow

document.onkeydown = function() {
    switch (window.event.keyCode) {
        case 37:
            alert('left');
            break;
        case 38:
            alert('up');
            break;
        case 39:
            alert('right');
            break;
        case 40:
            alert('down');
            break;
    }
};

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