time out function callback

function timeoutfunc(fn,delay) {
    var intv = setTimeout(function() {
        intv = null;
        fn(new Error("Timeout"));
    }, delay);

    return function() {
        // timeout hasn't happened yet?
        if(intv) {
            clearTimeout(intv);
            fn.apply(this, [].concat([].slice.call(arguments)));
        }
    };
}

// Dummy ajax call
var ajax = function(url, callback){
    setTimeout(function(){
        callback("From inside ajax");
    }, 4000);
};

function myCallback(message){
    console.log(message);
}

// If the callback doesnt return within 5000, call the 
// callback with error object
ajax('http://somewhere.com', timeoutfunc(myCallback, 5000);