I am trying to get resource from the some url, that resource is separated as multiple pages, the number of page is over 500, but the order of resource have to be guaranteed, so I decided to use Async module. 

```
function getData(page, callback){
    var url = "http://someurl.com/document?page="+page;
    // get data from the url ...
    // when success, 
    callback();
};

```

So, above function is get resource from some url, I have to iterate this function to many times, but I don't know how can I iterate this with async waterfall. What point I should push the **for** iteration? 

```
async.waterfall([

    // page 1 
    function(callback){
        getData(1, function(){
            callback(null);
        });
    },

    // page 2
    function(callback){
        getData(2, function(){
            callback(null);
        });
    },

    // page 3, 4, 5..... 100, ... 500

],function(err, result){
    if(err) return next();

    console.log('finish !');
});

```