How can I get an object’s absolute position on the page in Javascript? [duplicate]

var cumulativeOffset = function(element) {
    var top = 0, left = 0;
    do {
        top += element.offsetTop  || 0;
        left += element.offsetLeft || 0;
        element = element.offsetParent;
    } while(element);

    return {
        top: top,
        left: left
    };
};

(Method shamelessly stolen from PrototypeJS; code style, variable names and return value changed to protect the innocent)