Guides & Examples

Three small worked examples, copied and trimmed from the original README.

Example 1 — a logging plugin

The “Hello world” of asimov.js: a plugin that registers one initializer that logs a message.

asimov-log-message/
  lib/
    init/
      logMessage.js
  index.js
  package.json

module.exports = function initializer (next) {
  console.log('Hello world');
  next();
};

var asimov = require('asimov');
var logMessage = require('./lib/init/logMessage');

module.exports = function plugin () {
  asimov.init(logMessage);
};

module.exports.start = function bootstrap () {
  asimov.use(module.exports).start();
};

module.parent || module.exports.start();

Run it:

$ asimov
> Hello world

Example 2 — a custom CLI command

Add a loc command that counts lines of JavaScript code in lib/. Any project that installs this plugin gets asimov loc for free.

asimov-loc/
  lib/
    commands/
      loc.js
  index.js
  package.json

var asimov = require('../../index');

function countLinesInPath (path) {
  // walk path recursively, sum lines in every .js file
}

module.exports = function () {
  var path = process.cwd() + '/lib';
  var started = new Date();
  var count = countLinesInPath(path);

  asimov.logger.since('loc', 'Counted ' + count + ' lines in ' + path, started);
};

The CLI auto-discovers any file under lib/commands/, in your project and in each node_modules/* dependency. Project commands win over dependency commands of the same name.

Example 3 — a render sequence

This is how asimov-pages implements rendering. The sequence is named, then any plugin can push processors onto it.

asimov.addSequence('render');

asimov.render(function (page, next) {
  page.html = renderMarkdown(page.body);
  next();
});

asimov.render(function (page, next) {
  page.html = minify(page.html);
  next();
});

asimov.runSequence('render', somePage)
  .done(function (page) { writeFileSync(page.path, page.html); })
  .fail(function (err) { console.error(err); });

The key idea: processors don’t know about each other. Each one mutates the page and calls next(). New behaviours are added by new processors, not by editing existing ones.