How to grab the onSubmit event for a form?
Question
I want to know how to grab the onsubmit event from a form to do some form validation, because I don't have access to it directly. (I am writing a Wordpress plugin for comments, so don't have direct access to the form tag or the submit button.)
I got so frustrated trying to do this for my plugin that I have written a Hello World version below. I want it to show the 'Hello World' alert when I load the page, and the "form submitted" alert when I click on the submit button. Instead, it shows both pop ups when the page loads.
Here is my code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Hello World</title>
</head>
<body>
<h2>Test</h2>
<form action="#" method="post" id="commentform">
<p><input type="text" name="author" id="author" size="22" tabindex="1" />
<label for="author"><small>Name (required)</small></label></p>
<p><input name="submit" type="submit" id="submit" tabindex="5" value="Submit Comment" />
</form>
<script type="text/JavaScript">
<!--
alert("Hello world");
var formCheck = document.getElementById("commentform");
formCheck.onSubmit = doMapping();
function doMapping() {
alert("form submitted");
return false;
}
-->
</script>
</body>
</html>
3 answers
solution1
12 2009-04-02 15:51:19
Change this:
formCheck.onSubmit = doMapping()
to this:
formCheck.onSubmit = doMapping
When you add parenthesis to the end of a function you execute that function. When you assign a function (or pass it as a parameter to another function) you need to omit the parenthesis as that is the way to retrieve a function pointer in JavaScript.
Edit: You will also need to move the declaration of the doMapping function above the assignment of that function to the onsubmit event like this (good catch tvanfosson!):
function doMapping() {
alert("form submitted");
return false;
}
formCheck.onSubmit = doMapping();
However if the doMapping function is not used elsewhere you can declare the doMapping function as an anonymous function like this:
formCheck.onSubmit = function() {
alert("form submitted");
return false;
}
which seems a bit cleaner to me.
solution2
8 2009-04-02 15:54:31
Using jQuery.
$(document).ready( function() {
$('#commentform').submit( function() {
alert('form submitted');
return false;
});
});
solution3
0
Thank you! Actually I solved it another way, using both Andrew's suggestion and the window.onload event - I think the problem was partly because the element hadn't actually loaded.
window.onload = function(){
if (document.getElementById("commentform")){
document.getElementById("commentform").onsubmit = doMapping;
}
}
function doMapping(){
alert("form submitted");
return false;
}
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