Test whether a string representing an object n-levels deep is available
This maybe a matter of taste, but I'm not a big fan of slicing arrays.
I find this alternative implementation using a for loop and without array slicing a bit simpler:

function isAvailable(s,context) {
    var aSplit, ob, i;

    if (s === undefined || s === null) {
        return false;
    }

    aSplit = s.split('.');
    ob = context;
    for (i = 0; ob !== undefined &amp;&amp; i &lt; aSplit.length; ++i) {
        ob = ob[aSplit[i]];
    }
    return typeof ob === "object";
}