Question

Building my first “serious” Node.js project (using Express).

I need to use several calls to several REST APIs, collect all the results, massage them and return a complete JSON to the client (HTML5 + AJAX).

1. Call API A
2. Call API B
3. Call API A again (with results from B)
4. Process results from the 3 calls into a JSON
5. response.send(result)

I’m sure/hoping there’s an easy pattern, or solution, or module that I just didn’t google properly for 🙂
I’d also would appreciate an opinion on where to place such operations (under ‘routes’? Seperate files? etc.)

Thanks for your time!

Answer 1

The async module fits into this kind of job. Specifically, you may use the async.waterfall function.

Example:

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

Edit, if you have some nontrivial dependencies between the jobs, then you may use async.auto. It will determine the best order for running functions based on their requirements.