Use this to visualize the vibration result from the navigator.vibrate api.

navigator.vibrate-visualizer.js

(function (){
    const originalVibrate = navigator.vibrate;
    navigator.vibrate = function(){
        
        var timer = 0;
        var _b = document.body || false;
        var curToggleStatus = true;
        var previousBodyBorder = _b.style.border || 'none';

        function toggle (force) {
            if(!_b) return;
            if(curToggleStatus && !force){
                _b.style.border = 'solid 3px red';
            }else{
                _b.style.border = previousBodyBorder;
            }
            curToggleStatus = !curToggleStatus;
        }

        (arguments[0] || []).forEach(function(cur){
            setTimeout(toggle, timer);
            timer+= cur;
        });
        setTimeout(function(){toggle(true);}, ++timer);
        return originalVibrate.apply(navigator, arguments);
    }
})();

/*
// plays the imperial march
window.navigator.vibrate([500, 200, 500, 200, 500,
200, 100, 200, 100, 200, 500,
200, 100, 200, 100, 200, 500
]);
*/