unction checkDevTools(options) {const isFF = ~navigator.userAgent.indexOf("Firefox"); let toTest = '';if (isFF) { toTest = /./; toTest.toString = function() { options.opened(); } } else { toTest = new Image(); toTest.__defineGetter__('id', function() { options.opened(); }); } setInterval(function() { options.offed(); console.log(toTest); console.clear && console.clear(); }, 1000); } checkDevTools({ opened: function() { document.body.innerHTML = 'Dev Tools is on'; }, offed: function() { document.body.innerHTML = 'Dev Tools is off'; } });