前端跨域问题及解决方案
document.domain
// https://jestjs.io/ => document.domain is "jestjs.io"
// https://www.w3school.com.cn/ => document.domain is "www.w3school.com.cn"
// https://www.baidu.com/ => document.domain is "www.baidu.com"
// https://jestjs.io/ => document.domain is "jestjs.io"
// https://www.w3school.com.cn/ => document.domain is "www.w3school.com.cn"
// https://www.baidu.com/ => document.domain is "www.baidu.com"
