Updated: Just use .htaccess please, if you're using JavaScript there's something 100% wrong with your code.
window.location.href = window.location.protocol + "//www." + window.location.host
look at the location object for more info: https://developer.mozilla.org/en-US/docs/Web/API/Location
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.