Thursday, May 26, 2011

Developing and building RequireJS apps with a central code repository

Most of the projects I develop at work are enterprise Microsoft apps, using Visual Studio and Team Foundation Server. Reusing JavaScript in VS projects typically involves either copying the code (violating the DRY principle) or creating pre-build events to copy the code at build time (a little better, but far from ideal)


I’ve been doing a lot of JavaScript application development lately, and really loving James Burkes RequireJS module loader. For a recent project I ended up copying a non-trivial amount of common utilities code, and decided it was time to figure out a better method to centralize common JavaScript code without requiring a script server and related overhead (HTTP requests) and maintenance.


After some experimentation, and discussion with RequireJS author James Burke, I figured out how to develop and build RequireJS apps using a central repository for common JavaScript code. The basic gist is that you specify a HTTP path to the repository code modules during development, (a localhost website) from which the files are dynamically loaded, and a filesystem path (to the source of the localhost website) in the build configuration file. The RequireJS optimizer consolidates the common modules via the filesystem path, along with the local modules, into a single file for deployment.


This allows me to maintain and version control common JavaScript code in a single project, and use that code in separate projects, much the way I do with dll/project references in compiled languages like C#.

main.js with HTTP path(s):
require(
        {
            paths: {
                //various application path aliases
                “core”: “//localhost/ipayment.core.javascript/scripts/core”
            }
        },
        [
            //direct dependencies
        ],
        function (<dependency>) {
            <dependency>.<method>();
        }
);


app.build.js with filesystem path(s):
({
    appDir: “../”,
    baseUrl: “Scripts”,
    dir: “../../Build”,
    paths: {
        //various application path aliases
        “core”: “../../../iPayment.Core/iPayment.Core.Javascript/Scripts/Core”
    },
    optimize: “none”, //”uglify”, “closure” (Java Only), “closure.keepLines” (Java Only), “none”
    modules: [
        {
            name: “main”
        }
    ]
})


Cool!
Tim