Async.js waterfall (functions defined outside of the array)

Question

I am using async.js for the first time and would like to seperate out the function array into seperate functions. I have:

working code

    async.waterfall([
        function(callback)
        {
            var querySuccess = function (tx, result)
            {
                callback(null, result.rows.item(0).EventImportTime || "");
            };

            var queryError = function (tx, e)
            {
                callback("Query Error")
            };

            database.open();
            database.query("SELECT EventImportTime FROM Contact WHERE Contact.Id = ?", [contactId], querySuccess, queryError);
        },
        function(lastImportTime, callback)
        {
            var url = "";
            url += 'MobileGetvents.aspx?';
            url += '&LastImportTime=';
            url +=  lastImportTime;
            url += '&Format=JSON';

            callback(null, url)
        },
    ],
    function(err, result)
    {
        if (err)
            console.log("Error Happened");
        else 
        {
            console.log(result);
            getJSON(result, callback, 

errorCallback)
            }
        })

I want

async.waterfall([
            getLastImportTime(callback) ,
            buildUrl(lastImportTime, callback),
        ],
        //callback
);

However when I run this code it always returns

Uncaught ReferenceError: lastImportTime is not defined

Vincent Briglia · Accepted Answer · 2012-05-15 11:28:16Z

5

I would assume that you want this instead:

var getLastImportTime = function(callback) { };
var buildUrl = function(lastImportTime, callback) { };

async.waterfall([
            getLastImportTime,
            buildUrl,
        ],
        //callback
);

answered May 15, 2012 at 11:28

Vincent Briglia

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4 Comments

Jon Wells Over a year ago

haha learning something new can really make you overlook the obvious.

Vincent Briglia Over a year ago

If you really want to learn something hot, you should take a look at jQuery's Deferred object and most importantly, the pipe method, you can achieve the same thing as what asych waterfall does.

Jon Wells Over a year ago

believe it or not thats where this Async.js came from. I wanted to use deferred but couldnt figure it out. So i turned to Async.js

Vincent Briglia Over a year ago

This is an excellent article I found very helpful and triggered the 'AHA' moment for me: msdn.microsoft.com/en-us/magazine/gg723713.aspx

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