dom检测

form = document.createElement('form');
form.id = "angdh";
document.body.appendChild(form);
if(window["angdh"] !== form){console.log('被检测1')}
if(!("angdh" in window ) || window.hasOwnProperty('angdh')){console.log('被检测2')};
if(!(delete window['angdh'])){console.log('被检测3')};
if(window['angdh'] !== form){console.log('被检测4')}
if(Object.getOwnPropertyDescriptor(window,'angdh')){console.log('被检测5')};
window['angdh'] = 1;
if(window['angdh'] === form){console.log('被检测6')};
if(!Object.getOwnPropertyDescriptor(window,'angdh')){console.log('被检测7')};
delete window['angdh'];
if(window['angdh'] !== form){console.log('被检测8')}