Submit form conditionally - JavaScript by SiteArticles.com
In the long-gone days of the early Internet, having a form on the website was
tantamount to dabbling with "cutting-edge" technologies. Intricate Perl scripts
and esoteric CGI scripts were required to process those forms and people used
to suffer bouts of cold sweat whenever there manifested a need to use web
forms. To create a form-handling script used to be in the realms of MCAs and
computer engineers. No longer is it so. The Internet these days is replete with
all sorts of form handling scripts, and wherever you choose to host your
website, or for that matter even a web page, you can easily deploy a form
handling script and start interacting with your visitors.
As the level of interaction goes complex, you require more complicated scripts.
One way is to write a single script containing hundreds of lines of code. The
action script (that comes within <form ... action="scriptname.php">)
encompasses numerous if-then-else conditions, and even within these conditions,
there could be zillions of nested if-then-else conditions. After a certain time
it becomes a Herculean task to maintain such a form handling script and unless
you are an avid documenter, you'll lose the track in no time.
The second way is, write smaller scripts and let the form call them according
to the user input. This can save you hundreds of lines of coding, and even if
it doesn't, it makes things a lot easier. Suppose you have a form that, along
with other things, asks the visitor to which state she belongs. Then, when she
clicks the submit button, the action happens according the state she selected.
If you have a single script and if you want the script to act according to the
individual state, you might end up writing a very large action script. On the
other hand, if you specifically write a script for, let us say, California;
then you have to write code only centered around California and you can, for
the time being, forget about other states.
Javascript lets you submit a single form, conditionally, to different script.
Here, we'll learn how to achieve this. First, let us go through a simple form:
<form method="post" name="frm1" onSubmit="javascript: decide_action();"
action=""> <input type="radio" name="ch" value="one" /> Choice 1
<input type="radio" name="ch" value="two" /> Choice 2
<input type="radio" name="ch" value="three" /> Choice 3
<input type="submit" name="s1" value="Submit" /> </form>
As you can see, this form displays three radio buttons. The objective is, send
the form to a script according to the radio button selected. Since some
Javascript action needs to take place once the Submit button is clicked, we
invoke decide_action() function through the onSubmit attribute of the
<form> tag. Although we include the action attribute, it is left blank.
The other form fields are the usual ones. Now let us dive into the cryptic
world of the actual script that steers the submission.
<script language="javascript">
function decide_action() { if(check_buttons()==true) {
if(document.frm1.ch[0].checked==true) { document.frm1.action="one.php"; } else
if(document.frm1.ch[1].checked==true) { document.frm1.action="two.php"; } else
{ document.frm1.action="three.php"; } document.frm1.submit(); } }
function check_buttons() { var ok=false; for(i=0; i<3; i++) {
if(document.frm1.ch[i].checked==true) { ok=true; } } if(ok==false) {
alert("Select at least one option."); } return ok; }
</script>
This script contains two functions. The latter one, check_buttons(), makes sure
that you select at least one option because if you don't select an option,
Javascript doesn't know which form handling script to invoke. It first
initializes a variable, ok, to false:
var ok=false;
then through a loop it checks all the radio buttons of the form. As soon as it
encounters a radio button that is checked, it assigns the value true to ok
ok=true;
When the function, decide_action() encounters a true:
if(check_buttons()==true)
it first assigns a file name to the action attribute of the object frm1 (the
name of the form):
document.frm1.action=file_name;
and then calls the submit() function for that form:
document.frm1.submit();
The script uses multiple if-else decisions to check which radio button was
selected, and then submits the form to a form handling script accordingly.
Now, let us take both the functions: check_buttons() and decide_action() to the
next level. There can be varied number of radio buttons to check. Why just
limit to three radio buttons. The following code not only handles limitless
radio buttons, it also assigns the name of the file accordingly (the value of
the radio button should be the name of the respective action file).
<script language="javascript">
function decide_action() { var file_destination=check_buttons();
if(file_destination!="") { document.frm1.action=file_destination + ".php";
document.frm1.submit(); } }
function check_buttons() { var val=""; for(i=0; i<document.frm1.ch.length;
i++) { if(document.frm1.ch[i].checked==true) { val=document.frm1.ch[i].value; }
} if(val=="") { alert("Select at least one option."); } return val; }
</script>
This next version of the code is much smaller as it gets rid of multiple
if-else statements. Since a particular set of radio buttons is actually an
array, we can loop through the array to find out which button is checked. Then
we can store the value stored at that index location and return it to the
calling function -- decide_action(). decide_action() this time uses the value
returned, appends the extension ".php", assigns it to the action attribute and
then submits it.
This article has walked you through various concepts, but mainly, submitting
form to different scripts according to selections made in the form.
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