Question

I’m making my own jQuery validation plug in. What is the best method to select the input fields with an attribute of data-validate in the plugin? for clarification the plugin can be sent $('form').validate()
it possible it may be working on more than 1 form on a given page

new problem
so Im now using

    var options =  $.extend(defaults, options);
    return this.each(function() 
    {
    form=this;
    //lazy
    $(this).submit(function()
    {

        var o = options;
        $('['+o.attr+']', form).each(function()
        {
            var val=$(this).val()
            alert($(this).attr('name'))
        })
        //if errors
        //encapsulate error group
        //add to html with .after()
        return false;
        //no errors send
    })
    });

whats happening is that for some reason the plugin is only getting the last form. note I only have the main function of the plugin o.attr value is data-validate which works.
here is a link to the page im making it on http://yamikowebs.com/_test/project/

Answer 1

(function(){
    $.fn.myplugin = function(options) {
        return this.each(function(){ // <-- this part makes your function execute on every element passed to it
             $('input[data-validate]', this).each(function(){ // <-- this part iterates over all inputs with an attribute of "data-validate" in the current (", this" part) form
                 // do stuff here
             });
        });
    }
})(jQuery);

Usage:

$('form').myplugin();
//  |
//  |
//   --- If multiple forms are on the page, jQuery will pass all of them to your plugin

Further reading: jQuery Plugin Authoring.

Edit

Bonus: Working Fiddle to illustrate it all

Edit 2

Yikes, shouldn’t be on SO when tired. Updated answer and fiddle to actually answer the OP’s question.