Multiple single file builds using one "build script" for requirejs optimizer

builder.js

//Load the requirejs optimizer
var requirejs = require('./path/to/r.js'),
    //Set up basic config, include config that is
    //common to all the optimize() calls.
    basConfig = {
        baseUrl: './some/path',
        paths: {
            //whatever is neded globally.
        }
    };

// Function used to mix in baseConfig to a new config target
function mix(target) {
    for (var prop in basConfig) {
        if (basConfig.hasOwnProperty(prop)) {
            target[prop] = basConfig[prop];
        }
    }
    return target;
}

//Now do a series of builds of individual files, using the args suggested by:
//http://requirejs.org/docs/optimization.html#onejs

requirejs.optimize(mix({
    name: 'first/main/module',
    include: [/*if you need to include extra modules */],
    out: 'path/to/output/firstMain-built.js'
}), function (buildReportText) {
    //First build complete, start the next one.
    requirejs.optimize(mix({
        name: 'second/main/module',
        include: [/*if you need to include extra modules */],
        out: 'path/to/output/secondMain-built.js'
    }), function (buildReportText) {
        //all done.
    });
});

That's fine. In that case I'd switch this code around to define an array of spec objects, ala { name: 'foo', ... } then run them like so:

var specs = [spec1, spec2, spec3];  // assume specN's defined previously, elided for clarity

var async_runner = specs.reduceRight(function(prev, curr) {
  return function (buildReportText) { 
    requirejs.optimize(curr, prev);
  };
}, function(buildReportText) {} );

async_runner();

Is chaining definitely going to be the New World Order for this API? If so, I'll go ahead and switch my r.js driver generator around right now.

So that reduceRight will create an array of functions, each one, when called, will run a build. For me the magic part is still what async_runner() does. I feel like there is something missing from this code sample, something that steps through the functions in async_runner?

Is chaining definitely going to be the New World Order for this API? If so, I'll go ahead and switch my r.js driver generator around right now.

Yes, r.js will likely need to go to callback-based, async processing for the file issues, so if it is easier to switch now, then probably for the best. I do not expect to get to the async file IO issues until after 1.0.3. I may even wait for a 1.1.

reduceRight will create an array of functions

Not quite; this usage of reduceRight creates a function, actually a chain of nested functions, from an array of simple objects (the first parameters to requirejs.optimize). Note: I forgot to include the call to mix in my example above; let's just assume it's already been map'ped onto the spec objects. Expanding what my snippet would do, it'll create a function, async_runner, whose definition looks like this:

// Expansion of the reduceRight() call

var async_runner = function (buildReportText) {
  requirejs.optimize(spec1, function (buildReportText) {
    requirejs.optimize(spec2, function (buildReportText) {
      requirejs.optimize(spec3, function (buildReportText) {});
    });
  });
}

Knowing that we don't actually use the buildReportText parameter on the outermost function, we can invoke the whole nested mess with a call like async_runner().

This approach rather cleanly abstracts the interesting core data (here, a sequence of input parameters) from the rather hairy code that consumes that data.

James, check out this gist for a little example that you can run in node to play with this idea.

Thanks for the heads-up. requirejs-rails on the precompilation branch has been updated for this change. See rjs_driver.js.erb on the branch.

@whitley, neat use of reduceRight, thanks for the explanation. Nice approach to know in general for repeated async calls.