• 避免在iframe上执行js，return需要配合外面的function

if (window.top != window.self){//don't run on frames or iframes
    confirm('Detected iframe, now return.');
    return;
}

• 找回alert，反击名字被重定义

(function(){//召唤alert
    var temp_frame = document.createElement('iframe');
    document.body.appendChild(temp_frame);
    window.fuck = temp_frame.contentWindow.alert;
})()

• 测试时间以判断性能

console.time();
for(let i=0;i<10000;i++){
  //code
}
console.timeEnd();