streamlinejs

streamline.js streamline.js is a language tool to simplify asynchronous Javascript programming. tldr; See Cheat Sheet Instead of writing hairy code like: function archiveOrders(date, cb) { db.connect(function(err, conn) { if (err) return cb(err); conn.query("select * from orders where date < ?", [date], function(err, orders) { if (err) return cb(err); helper.each(orders, function(order, next) { conn.execute("insert into archivedOrders ...", [order.id, ...], function(err) { if (err) return cb(err); conn.execute("delete from orders where id=?", [order.id], function(err) { if (err) return cb(err); next(); }); }); }, function() { console.log("orders have been archived"); cb(); }); }); }); } you write: function archiveOrders(date, _) { var conn = db.connect(_); conn.query("select * from orders where date < ?", [date], _).forEach_(_, function(_, order) { conn.execute("insert into archivedOrders ...", [order.id, ...], _); conn.execute("delete from orders where id=?", [order.id], _); }); console.log("orders have been archived"); } and streamline transforms the code and takes care of the callbacks! No control flow APIs to learn! You just have to follow a simple rule: Replace all callbacks by an underscore and write your code as if all functions were synchronous. Streamline is not limited to a subset of Javascript. You can use all the features of Javascript in your asynchronous code: conditionals, loops, try/catch/finally blocks, anonymous functions, chaining, this, etc. Streamline also provides futures, and asynchronous variants of the EcmaScript 5 array functions (forEach, map, etc.). News The latest cool feature is TypeScript support. See https://github.com/Sage/streamlinejs/wiki/TypeScript-support for details. Streamline 1.0 was a major revamp as a Babel Plugin. Streamline 2.0 was a smaller step from Babel 5 to Babel 6. See https://github.com/Sage/streamlinejs/wiki/Babel-upgrade for details. Installation NPM, of course: npm install streamline -g The -g option installs streamline globally. You can also install it locally (without -g) but then the _node and _coffee commands will not be in your default PATH. Note: If you encounter a permission error when installing on UNIX systems, you should retry with sudo. Warning: you may get errors during install because fibers is now installed as an optional package and it may fail to build. But this package is optional and streamline itself should install fine. Hello World Streamline modules have ._js or ._coffee extensions and you run them with _node or _coffee. Example: $ cat > hello._js console.log('hello ...'); setTimeout(_, 1000); console.log('... world'); ^D $ _node hello You can also create standalone shell utilities. See this example. Compiling and writing loaders You can also set up your code so that it can be run directly with node or coffee. You have two options here: The first one is to compile your source. The recommanded way is with babel's CLI (see babel-plugin-streamline). But you can still use streamline's CLI (_node -c myfile._js or _coffee -c myfile._coffee) The second one is to create a loader which will register require hooks for the ._js and ._coffee extensions. See this example. Compiling will give you the fastest startup time because node will directly load the compiled *.js files but the registration API has a cache option which comes close. The recommandation is to use the loader during development but deploy precompiled files. Runtime dependencies The runtime library is provided as a separate streamline-runtime package. If you deploy precompiled files you only need streamline-runtime. If your application/library uses a loader you will need to deploy both streamline-runtime and streamline with it. Browser-side use You have two options to use streamline in the browser: You can transform and bundle your files with browserify. See how the build.js script builds the `test/browser/*-test.js files for an example. You can also transform the code in the browser with the transform API. All the necessary JS code is available as a single lib/browser/transform.js file. See the streamlineMe example. Generation options Streamline can transform the code for several target runtimes: callbacks. The transformed code will be pure ES5 code. It should be compatible with all JavaScript engines. fibers. The transformed code will take advantage of the fibers library. This option is only available server-side. generators. The transformed code will take advantage of JavaScript generators. It will run in node.js 0.12 (with the --harmony flag), in node.js 4.0 (without any special flag) and in latest browsers. await. The transformed code will take advantage of ES7 async/await. The choice of a target runtime should be driven by benchmarks: The fibers mode gives superior development experience (because it uses real stacks for each fiber so you can step over async calls). It is also very efficient in production if your code traverses many layers of asynchronous calls. The callbacks transform is obtained by chaining the generators transform and the regenerator transform. It is less efficent than the generators transform and we recommend that you use generators if generators are supported by your target JavaScript engine and that you only use callbacks if you target a legacy JavaScript engine. The await mode is experimental at this stage. It relies on an emulation as async/await is not yet available natively in JavaScript engines. You can control the target runtime with the --runtime (callbacks|fibers|generators|await) CLI option, or with the runtime API option. Interoperability with standard node.js code You can call standard node functions from streamline code. For example the fs.readFile function: function lineCount(path, _) { return fs.readFile(path, "utf8", _).split('\n').length; } You can also call streamline