Nick Berardi’s Coder Journal

Today I had the need to create a custom event using jQuery, in order to launch a customized form validation event from a global submit event. I did this so I could focus in on the first form field that had an error. My event from the global.js script, that is included on every page of IdeaPipe, looks like this:

$("form").submit(function () {
	var valid = $(this).validate();

	// if the form didn't validate then focus the input on the first error
	if (!valid)
		$(this).find(":input[error]:first").focus();

	return valid;
});

This is pretty standard jQuery. What this code above does is set a custom function for the submit event for any <form /> tag on the page. The submit event will only be allowed to continue if a return value of true is returned from the function.

I was able to create this custom jQuery event with the following code:

jQuery.fn.extend({
	validate: function (fn) {
		if (fn) {
			return jQuery.event.add(this[0], "validate", fn, null);
		} else {
			var ret = jQuery.event.trigger("validate", null, this[0], false, null);

			// if there was no return value then the even validated correctly
			if (ret === undefined)
				ret = true;

			return ret;
		}
	}
});

There are two different states to this method. Primarily because in JavaScript all parameters are optional for functions. So the two states of this function are:

• validate(fn) - sets the event
• validate() - fires the event

An example of setting the event is:

$("form.user-login").validate(function () {
	var userNameValid = ValidateLoginUserName();
	var passwordValid = ValidateLoginPassword();

	return userNameValid && passwordValid;
});

In this example the form is valid if both the login user name and password validate.

An example of using the event is the same as the method above.

$("form").submit(function () {
	var valid = $(this).validate();
	// do some stuff
	return valid;
});

This may not be the standard bind() and trigger() that most jQuery programmers are use to, but I needed an event that would return a value of true or false, so that I my submit event handler knows if it should focus on errors or continue the submit process.

Hope everybody finds this useful.

Tags: IdeaPipe, JavaScript, jQuery

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This entry was posted on Friday, May 23rd, 2008 at 12:13 pm and is filed under How To, JavaScript. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.