Javascript for a form on the server-side?

Question

The question emerges from the discussion with Christoph in my last question 'HTML: target=”_blank” for a drop-down list' and the alternative method by Andrew.

Problem: to run code server-side because some users lack Javascript support. The situation is a form like here.

Some suggestions:

Christoph's recommendation:

<form action="path-to-redirection-script" method="GET" target="_blank"
 onsubmit="window.open(this.elements['foo'].value); return false;">
 <select name="foo" size="1">
  <option value="http://google.com">google</option>
 </select>
 <input type="submit" value="go">
</form>

Alternative method by Andrew:

<form onsubmit="this.js_enabled.value=1;return true;">
    <input type="hidden" name="js_enabled" value="0">
    <input type="submit" value="go">
</form>

Question: How would you do the server-side scripting in the case of form?

Gab Royer: I will outline the suggestions. C's method relies totally on the server, fetching the script each time from the server. In contrast, A's method fetch the code only from the server if the user has no JS support. Otherwise, client runs the JS. — Léo Léopold Hertz 준영
– Léo Léopold Hertz 준영, Commented Jul 13, 2009 at 23:29
What kind of scripting languages are you permitted to use on your server? — Chris W. Rea
– Chris W. Rea, Commented Jul 13, 2009 at 23:35
Sorry SimpleThings I deleted my comment because I was a bit ashamed not to understand the question as it didn't seem that hard for other people... But thanks a lot for sorting it out! — Gab Royer
– Gab Royer, Commented Jul 14, 2009 at 0:00
@SimpleThings: the server-side script only gets calles if scripting is disabled: see my answer for details — Christoph
– Christoph, Commented Jul 14, 2009 at 9:07

Community · Accepted Answer · 2017-05-23 10:32:52Z

2

Actually, it depends on the server-side language you're going to use.

But, it's as simple as reading out the values in the POST and GET Values the Form delivers you.

i.e. PHP:

if($_POST["js_enabled"] == 0)  
{  
   doSomething(); // Redirecting   
}

But don't forget to validate all values.

good luck,
rAyt

Edit

There you go (pretty good answer though)

How are POST and GET variables handled in Python?

edited May 23, 2017 at 10:32

CommunityBot

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answered Jul 13, 2009 at 23:23

Henrik P. Hessel

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4 Comments

Léo Léopold Hertz 준영 Over a year ago

a small problem, my admin does not allow PHP. (Please, do not remove your answer. It may be useful to others with PHP support.)

barrowc Over a year ago

What server-side scripting options does your admin allow?

Léo Léopold Hertz 준영 Over a year ago

barrowc: cwrea: zsh, python and lua.

Henrik P. Hessel Over a year ago

I would recommend you python. kinda strange though that php isn't allowed :)

Christoph · Accepted Answer · 2009-07-14 09:06:36Z

1

There's no need for any additional code or checking for scripting on the server side: Because of the return false in the onsubmit handler, the form won't be submitted if the handler is executed!

Returning false from event handlers supresses the default action associated with the event the same way as calling event.preventDefault() (event.returnValue = false in IE) does.

answered Jul 14, 2009 at 9:06

Christoph

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8 Comments

Léo Léopold Hertz 준영 Over a year ago

Situation: onsubmit="window.open(this.elements['foo'].value); return false;"

Léo Léopold Hertz 준영 Over a year ago

If JS support, it opens a Window and return false so the server must process the code.

Léo Léopold Hertz 준영 Over a year ago

But it is the same with JS support. I probably misunderstood something.

Christoph Over a year ago

@SimpleThings: if JS is enabled, the return false will suppress the default action, ie the form won't be submitted, ie the server-side script won't be called

Léo Léopold Hertz 준영 Over a year ago

Situation: <form action="path-to-redirection-script" method="GET" target="_blank" onsubmit="window.open(this.elements['foo'].value); return false;">

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