loop moving div from left to right

HTML

<!-- loop moving div from left to right -->
<div id="box">
</div>

CSS

#box{
    position:absolute;
    width:50px;
    height:50px;
    background-color:red;    
}

JavaScript

function loop() {
 //moving  div from left to right 
    $( "#box" ).animate({ "left": "+=5" }, 7000 , 'linear',
                        function() {loop();
        })
}
    loop();