_extract = function(o, what) {
    var count = (what === 2), out = (count) ? 0 : [], i;

    for (i in o) {
        if (owns(o, i)) {
            if (count) {
                out++;
            } else {
                out.push((what) ? o[i] : i);
            }
        }
    }

    return out;
}
Extracts the keys, values, or size from an object

@method _extract
@param o the object.
@param what what to extract (0: keys, 1: values, 2: size).
@return {boolean|Array} the extracted info.
@static
@private