JavaScript revocable function

function revocable(f) {
    return {
        invoke: function () {
            return f.apply(this, arguments);
        },
        revoke : function () {
            f = null;
        }
    };
}

var temp = revocable(console.log);
temp.invoke('1');  // logs
temp.revoke();
temp.invoke('2');  // throws

// Works in FF, apparently Chrome has a bug...  hmmm better ways to do this i think
// use with timeout to allow access 
// to a fuction for a set period of time

JS Fiddle:  http://jsfiddle.net/stevenhollidge/tKC5Q/