javascript - How to create simple jQuery plugin?

Question

This test plugin, is supposed to work like this: When an element is clicked, it moves down. Simple as that.

jQuery.fn.moveDown = function(howMuch){
    $(this).css("border", "1px solid black");
    $(this).click(function(){

        $(this).css("position", "relative");
        $(this).animate({top: '+='+howMuch});
    }); 
}

The problem is, when an element is clicked, it not only moves the clicked element but also ALL the other elements which the plugin was applied to.

What is the solution for this?

Answer 1

For plugin authoring try this way, much more solid:

Edit: Here is working jsFiddle example.

---

PLUGIN:

(function($){
    $.fn.extend({
        YourPluginName: function(options) {
                var defaults = {
                      howMuch:'600',
                      animation: '',//users can set/change these values
                      speed: 444,
                      etc: ''
                }
        };

       options = $.extend(defaults, options);

       return this.each(function() {
          var $this = $(this);              
          var button = $('a', $this);// this represents all the 'a' selectors;
                                            // inside user's plugin definition.

          button.click(function() {
            $this.animate({'top':options.howMuch});//calls options howMuch value
          });
       });
})(jQuery);

USER'S DOCUMENT:

$(function() {
   $('#plugin').YourPluginName({
     howMuch:'1000' //you can give chance users to set their options for plugins
   });
});

<div id="plugin">
  <a>1</a>
  <a>2</a>
  <a>3</a>
</div>