Waiting until async call is done to proceed in Node

Question

I'm trying to build a bot cluster, and I'm having some trouble here.

I'd like to call the following function, called BuildABot.

http://pastebin.com/zwP7rZay

Now after this call is finished, I'd like to call requestItems, which takes in the steamOffers object as a parameter.

http://pastebin.com/jsJ4fhwG

However, the object is null, because the call hasn't finished.

Is there any way to halt the call until buildABot is done?

Answer 1

There are various ways to handle your requirement, I will mention 2 options while I am sure you can find more. You may find many more examples all over the web.

Option 1: Using a callback function -

Pass a callback function to the async function, When async function is finished it will call the callback func. This way the code in the callback func will be executed only when async call is over.

Related topic - how-to-write-asynchronous-functions-for-node-js

Option 2: If you have more complicated logic and you want to perform one part after another you can use the async waterfall. Code example:

async.waterfall([
    function(callback){
        callback(null, 'one', 'two');
    },
    function(arg1, arg2, callback){
      // arg1 now equals 'one' and arg2 now equals 'two' 
        callback(null, 'three');
    },
    function(arg1, callback){
        // arg1 now equals 'three' 
        callback(null, 'done');
    }
], function (err, result) {
   // result now equals 'done'     
});

See async module site for more information.