Return first defined value from argument list.

firstDefined.js

/*!
 * Return the first defined value from argument
 * list. Vars must be declared before passing 
 * to the function - set equal to self to catch 
 * any existing value for that var name. Useful
 * for fetching values from an outer scope that
 * may or may not be defined yet, while providing
 * a fallback of a known (explicitly) defined value.
 *
 * // vars declared and assigned to self
 * var foo=foo, bar=bar;
 * var name = firstDefined(foo, bar, 'Bob');
 * // returns 'Bob' since foo and bar are undefined
 */
function firstDefined() {
    var undefined, i = -1;
    while (++i < arguments.length) {
        if (arguments[i] !== undefined) {
            return arguments[i];
        }
    }
    return undefined;
}