How to handle the non-js environment?

Let say I have a web page, index, and have a button can login, when I click login, the webpage become the login page,..... Here is what the web look like:

[     Banner      ]
[     Main        ]
[     Footer      ]

The site have 3 parts, Banner, Main and Footer. When user login, I change the main div to login, via an ajax call:

[     Banner      ]
[     Login       ]
[     Footer      ]

It works great, but if the NON-JS environment, I need to render the 开发者_运维百科whole page. What should I do the best to handle it is the most common way? Thank you.

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If 'NON-JS environment' means disabled or not supported javascript, use NOSCRIPT tag block. See in MDN, in MSDN

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If you want this to work correctly without JS, you'll need to handle rendering without AJAX. Depending on your backend you could try to reroute to a new page containing the correct content after successful login.