Since Javascript is often used for checking data a user puts into a form on a web page: Do the following: *Explain how J

[answerhappygod]

Since Javascript is often used for checking data a user puts
into a form on a web page: Do the following:
*Explain how Javascript can be called when a form is submitted,
and how it can access the form element data.
*Even though input data can be checked on a server, why would
you be likely to use Javascript for checking forms? Then even
though you have double-checked, why would you still double-check
the server code?