Question

I have a set of async functions that issue executeSql commands to drop 2 tables, and have callbacks to create the 2 tables and populate the 2 tables.

I’d like to know when they have ALL completed.

I wouldn’t mind if they executed synchronously. In fact, I’d prefer that they ran synchronously!

Q: Would I use the jQuery pipe method to queue up these functions so that they execute in a more traditional way than issuing callbacks?

I want to do something like:

DropTableA();
CreateTableA();
PopulateTableA();
DropTableB();
CreateTableB();
PopulateTableB();
window.location.replace('Index.htm');

Answer 1

Have a look at jQuery’s Deferreds and Promises.

In short, here’s an example of an async function that executes something asynchronously (setTimeout in this case). When calling the function you get back a promise.

var myFunc = function (value) {
    var d = $.Deferred();

    setTimeout(function () {
        d.resolve(42 * value);
    }, 1000);
    return d.promise();
};

var promise = myFunc(100);
promise.done(function (res) { console.log(res); });

You can use $.when to execute something when all promieses have been fulfilled, i.e.

$.when(p1, p2, p3).then(...)

If you want to execute them in order you can chain the deferreds using the deffered’s pipe.