Get position/offset of element relative to a paren

Question

I'm used to working with jQuery. In my current project however I use zepto.js. Zepto doesn't provide a position() method like jQuery does. Zepto only comes with offset().

Any idea how I can retrieve the offset of a container relative to a parent with pure js or with Zepto?

Answer 1

Example

So, if we had a child element with an id of "child-element" and we wanted to get it's left/top position relative to a parent element, say a div that had a class of "item-parent", we'd use this code.

var position = $("#child-element").offsetRelative("div.item-parent");
alert('left: '+position.left+', top: '+position.top);

Plugin Finally, for the actual plugin (with a few notes expalaining what's going on):

// offsetRelative (or, if you prefer, positionRelative)
(function($){
    $.fn.offsetRelative = function(top){
        var $this = $(this);
        var $parent = $this.offsetParent();
        var offset = $this.position();
        if(!top) return offset; // Didn't pass a 'top' element 
        else if($parent.get(0).tagName == "BODY") return offset; // Reached top of document
        else if($(top,$parent).length) return offset; // Parent element contains the 'top' element we want the offset to be relative to 
        else if($parent[0] == $(top)[0]) return offset; // Reached the 'top' element we want the offset to be relative to 
        else { // Get parent's relative offset
            var parent_offset = $parent.offsetRelative(top);
            offset.top += parent_offset.top;
            offset.left += parent_offset.left;
            return offset;
        }
    };
    $.fn.positionRelative = function(top){
        return $(this).offsetRelative(top);
    };
}(jQuery));

Note : You can Use this on mouseClick or mouseover Event

$(this).offsetRelative("div.item-parent");