animating a div based on its existing position

I am trying to animate a div -1500px every time my .btn-arrow button is clicked by grabbing the current position of #content

  var $offset = $('#content').offset.left()-1500;
    $('.btn-arrow').click( function(){ 
            $('#content').animate({marginLeft:$offset}); return false;
    });

<div style="margin-left: 0px; width: 99999px;" id="c开发者_JAVA技巧ontent">content </div>

Its not working though currently, any ideas anyone?

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you need the correct sytax:

 {marginLeft:'-=1500'}

(mind the quotes and the -= that animates relative to the current value.

you don't need to use the offset.

but I guess you need :

{left:'-=1500'}

in this case

more here

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offset() method returns offset object not the actual offset value.

the object returned by offset() method has two properties, left and top

so what you want to do is $offset.left - 1500

check the offset@jQuery API reference

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offset is an object not a value. Access with offset.left and offset.top.