Summary of JavaScript methods to verify whether the browser supports JavaScript_javascript skills

Effect:

Let’s first take a look at how other websites do it:
Google.com login: Both the client and server are verified, and a message is prompted The same
baidu.com login: the password input box is blocked
http://fanfou.com/register: both the client and the background are verified, but the information prompts are different
http:/ /login.xiaonei.com/Login.do: There is a prompt message after the user disables JS
My implementation steps:
Thoughts:
1, by default (js is disabled) the submit button is not displayed, if it is enabled After that, the submit button
2 is displayed, and the prompt information is displayed through
Code: