September 30th, 2010 – by Kris Zyp
For developers that are creating libraries and modules, it is generally preferable to make your code available to as broad of range of users as possible. There are several different module formats in JavaScript (a module is an encapsulation of code that draws on other modules). Picking one format is often mutually exclusive to the other formats. However, in this post I want to demonstrate how you can write JavaScript modules that can be used with multiple module loaders using some simple boilerplate. Of course not all the module loaders necessarily make sense for all modules. If you are writing a module that relies on the Node file system API, it only needs it to work with the NodeJS/CommonJS module format. Likewise, a DOM-based module wouldn’t need to run on Node.
Here we’ll deal with the actual module format, the mechanism of specifying dependencies and exporting or returning functions from the module that can be used by the users. This does not deal with the normalization of the actual APIs of the underlying system, although you might want to take a look at promised-io if you would like normalization of IO interaction across the browser, Node, and Rhino/Narwhal.
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Tags: and Persevere 2.0, modules, nodules, pintura, promosed-io, RequireJS, Server-Side JavaScript
Posted in CommonJS, Dojo | 5 Comments
September 20th, 2010 – by Kris Zyp
Promises are a well-established mechanism for modeling future or asynchronous actions. Promises allow asynchronicity while maintaining the core programming principles of composability and encapsulation. Writing asynchronous code in JavaScript can often be a confusing exercise due to the extensive need for callbacks, but promises help to define composable units of asynchronicity to encapsulate actions and reliably separate caller and callee’s concerns.
Promised-IO
Promised-IO utilizes promises as an abstraction for I/O operations on top of Node, Narwhal/Rhino, and the browser (where possible). This serves two purposes. First, this package provides the benefits of promise usage: clean separation of concerns and proper encapsulation of eventual values. Second, Promised-IO provides a consistent normalized interface for I/O that will work on multiple platforms without sacrificing any of the advantages of asynchronous I/O, making it easy to build modules that can be used by developers on many platforms.
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Tags: and Persevere 2.0, narwhal, node, nodejs, pintura, Server-Side JavaScript
Posted in CommonJS, Persevere | 11 Comments
September 15th, 2010 – by Kris Zyp
Nodules is a module loader for Node that provides a powerful set of features for application development and distribution. Nodules was written to solve the two major missing pieces of functionality I needed for efficient application development: flexible dependency resolution and module reloading. Nodules runs on top of Node’s simple base module loader, and nicely compliments the base loader with additional functionality. Furthermore, it provides this functionality using idiomatic asynchronous techniques, a smart package layout, and powerful module reloading.
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Tags: and Persevere 2.0, narwhal, node.js, nodules, pintura, Server-Side JavaScript
Posted in CommonJS, Persevere | 2 Comments
May 9th, 2010 – by Kris Zyp
The REST architecture has become increasingly recognized for its value in creating scalable, loosely coupled systems. REST is presented as a network interaction architectural style, not a programming methodology. However, the principles of REST can actually be very meaningfully and beneficially applied in the programming realm. We will look at how the resource oriented approach of REST can be applied as principles for programming language usage and design. The motivation for looking at REST should be clear. Little in history has been as ridiculously successful and scalable as the web, and REST is a retrospective look at the principles that were employed in designing the core technologies of the web, particularly HTTP. Applying such proven principles to our application design will certainly be beneficial.
Roy Fielding‘s REST architecture is broken down into seven constraints (and the four sub-constraints of the uniform interface). The individual concepts here are certainly not new, but collectively looking at these concepts as resource oriented programming may provide an interesting new perspective. I will also look at how these principles are exemplified in Persevere 2.0 in its object store framework, Perstore, and its web stack Pintura.
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Tags: and Persevere 2.0, Dojo, Persevere, pintura, rest, Server-Side JavaScript
Posted in Dojo, JavaScript, Persevere, thoughts | 1 Comment
March 2nd, 2010 – by Kris Zyp
CommonJS Utils is a collection of general purpose CommonJS-compliant modules. These modules can be used on Narwhal, Node, and other CommonJS platforms. The modules include:
- json-schema.js – This is a JSON Schema validator module. It can be used to validate data structures using JSON schema definitions. For example:
var validate = require("json-schema").validate;
var data = {name: "Test"};
var schema = {
properties: {
name: {type: "string"},
age: {type: "number"}
}
};
var validation = validate(data, schema);
validation.valid -> false
validation.errors -> indicates that age was not provided
data.age = 30;
var validation = validate(data, schema);
validation.valid -> true
This module also supports using standard native constructors as type definitions. The schema above could be written
more briefly:
var schema = {
properties: {
name: String,
age: Number
}
};
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Tags: and Persevere 2.0, CommonJS, CommonJS Utils, pintura, Server-Side JavaScript
Posted in CommonJS | 4 Comments
