jquery animation repeated several times
<p>I have a problem with the animation. Here is my code:</p>

<pre><code>&lt;html&gt;
    &lt;head&gt;
        &lt;script type='text/javascript' src='http://code.jquery.com/jquery-1.9.1.js'&gt;&lt;/script&gt;
        &lt;title&gt;title&lt;/title&gt;
        &lt;style&gt;
            div{
                width: 100px;
                height: 100px;
                background-color: green;
                position:relative;
                left: 0px;
            }
        &lt;/style&gt;
    &lt;/head&gt;
    &lt;body&gt;
        &lt;h1&gt;Animation&lt;/h1&gt;
        &lt;select id='text_1' type="text"&gt;
            &lt;option&gt;100&lt;/option&gt;
            &lt;option&gt;200&lt;/option&gt;
            &lt;option&gt;300&lt;/option&gt;
            &lt;option&gt;400&lt;/option&gt;
            &lt;option&gt;500&lt;/option&gt;
            &lt;option&gt;600&lt;/option&gt;
            &lt;option&gt;700&lt;/option&gt;
            &lt;option&gt;800&lt;/option&gt;
            &lt;option&gt;900&lt;/option&gt;
            &lt;option&gt;1000&lt;/option&gt;
        &lt;/select&gt;
        &lt;button&gt;Animate Div&lt;/button&gt;&lt;br/&gt;&lt;br/&gt;
        &lt;div&gt;&lt;/div&gt;
        &lt;script&gt;
            $(document).ready(function(){
                var number = 500;
                $('#text_1').bind('change', function(){
                    var number_2 = $('#text_1').val() != '' ? $('#text_1').val() : 500;
                    animation(number_2);
                });
                animation(number);
            });
            function animation(num){
                $('button').click(function(){
                    $('div').animate({
                        'left': num+'px',
                    }, 1000).animate({
                        'left': '0px',
                    }, 1000);;
                });
            }
        &lt;/script&gt;
    &lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>When I change select option (example: 300) and click the button, then does a two animations.
when I change select option again, then does a tree animations.
What is wrong. Please help.</p>
