passing value to a fadeOut callback function

what i'm trying to do is to get a recordset of logos, have to arrays. 1: for the display 2: for the bank

i will display 10 logos on delay i will replace them. with the next 10 from the bank

for (var i=0;i<=10;i+=1){
    $("#footerlogo-"+(i+1)).hide().append(DisplayArr[i]).fadeIn();
}


function ReplaceFooterLogos() {
    var runon = 0;
    var tempholder = "";
    for (var i=0;i<=10;i+=1){
        $("#footerlogo-"+(i+1)+"").fadeOut("fast",function(i){
            BankArr.push(DisplayArr.shift());
            DisplayArr.unshift(BankArr.shift());
            $(this).html(DisplayArr[i]).fadeIn()
        });
    }
    $("#mycaro开发者_如何学JAVAusel").delay(5000,function() { ReplaceFooterLogos() });
}

$("#mycarousel").delay(5000,function() { ReplaceFooterLogos() });

ignoe the delay function - i have it!

my question is why my the variable i is undefined? and how do i pass values to a callback?

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my question is why my the variable i is undefined?

I suspect you'll find that it's DisplayArr[i] that's undefined. i should be 11 when the callbacks run.

When you create a closure (which is what your fadeOut callback is), it has an enduring reference to a variable, not a copy of the value of the variable at that point in time. So all of your callbacks will see the same i value, which will be its value after the loop is finished (11). I'm guessing there's no DisplayArr[11]. (More about closures here: Closures are not complicated.)

Here's how you can fix it:

function ReplaceFooterLogos() {
    var runon = 0;
    var tempholder = "";
    for (var i=0;i<=10;i+=1){
        $("#footerlogo-"+(i+1)+"").fadeOut("fast", createCallback(i));
    }
    $("#mycarousel").delay(5000,function() { ReplaceFooterLogos() });

    function createCallback(index) {
        return function(index){
            BankArr.push(DisplayArr.shift());
            DisplayArr.unshift(BankArr.shift());
            $(this).html(DisplayArr[index]).fadeIn();
        };
    }
}

What we do there is use a factory function to build your fadeOut callback, using its index argument rather than i. The callback will close over the index argument that was given to createCallback for the call that created the callback (so, a different one for each callback), and so it will use the value for that iteration of the loop (0...10 inclusive).