3.1.2 • Public • Published


Weave your wefts betwixt the warps of loom generators and scaffolds.

wefts and warps

Loom makes it easy to share best-practices and common patterns for app development.

  • build a set of generators for public consumption based on some framework or library (like ember, angular, backbone, etc.)
  • consume those sets of generators
  • override those generators
  • build your own generators for your specific app

Using Loom Generator Packages from npm

Using generator packages from npm is easy:

npm install loom-ember --save
npm install loom-ember-qunit --save
generate controller user name:string age:number

Then refer to the documentation for the generators you've installed.

You must install with --save or add the module to your package.json instead (that's how loom knows how to use them).

If two generator sets respond to the same commands, they will both be run, allowing authors and consumers to compose them.

Create New Project Scaffolds with originate

In addition to generator sets, full project scaffolds are a simple command away when an author publishes a project to npm with a name matching originate-*.

For example:

npm install -g loom
originate ember my-new-app

Read more about originate.

Creating Your Own Generators

Also, see the full generator API below

While using generators others have created for you is great, its awesome to have a simple way to make generators for our own apps. Even if you're using a set of generators from npm, defining your own generators will override them.


npm install loom -g
generate --init


Initializing loom simply creates some directories in your project. After that, all you need is a template in ./loom/templates/:

Lets say we have a lot of "meal" objects in our app, lets make a template for what one of these objects looks like:


function {{objectName}}() {
  this.food = '{{params.food}}';
  this.venue = '{{params.venue}}';

And then you can generate files based on the template:

generate app/meal.js lunch food:taco venue:cart

This will create a file at app/lunch.js that looks like:

function lunch() {
  this.food = 'taco';
  this.venue = 'cart';

Loom, by default, will save files to your app in the same relative location they were found in your templates directory.


We can define a generator to make everything a little nicer. First we'll create a present method that determines what data goes to the template. Then we'll tell it where to find the template so we can simplify the generator command.


exports.present = function(next, env) {
  var locals = env.params;
  var name = env.args[0];
  locals.constructorName = name.charAt(0).toUpperCase() + name.slice(1);
  return locals;
exports.template = 'app/meal.js.hbs';

Now our template is simpler, no more {{params.food}} and it capitalizes our constructor like a proper lady or gent.


function {{constructorName}}() {
  this.food = '{{food}}';
  this.venue = '{{venue}}';

And finally our command is simpler, it now just matches a generator named meal instead of a template found at app/meal.js.

generate meal lunch food:taco venue:cart


The default generator uses handlebars, but we can swap it out for ejs by creating a very simple "engine":


var _ = require('underscore');
// module.exports = _.template
// that works, but for clarity:
module.exports = function(src, locals, callback) {
  callback(_.template(src, locals));

Rename your template to meal.js.ejs and edit it:

function <%= constructorName %>() {
  this.food = '<%= food %>';
  this.venue = '<%= venue %>';

Update your generator to point to the proper template:

exports.template = 'app/meal.js.ejs';

Loom looks at the file extension of the template (in this case ejs) and then tries to find a template engine named ejs.js.

Now generate your newly configured template:

generate meal lunch food:taco venue:cart

Multiple templates for one generator

Its very common for a generator to create several files, like unit tests and scaffoling. Lets add a unit test template to our meal generator.


describe('<%= constructorName %>', function() {
  it('sets food to "<%= food %>"', function() {
    var meal = new <%= constructorName %>();
    expect(meal.food).to.equal('<%= food %>');

And add the template path to your generator, note the rename from exports.template to export.templates.

exports.templates = [

Both templates will get the same data from generator.present and the files will be saved to the same relative path in your app as they are defined in your templates directory.

Default Generators

If you define loom/generators/default.js, loom will use it when a specific generator is not found.

Publishing Generators to npm for Everybody

Name your module loom-<name> (like loom-ember), place generators, templates, and engines in ./loom, and then publish. That's it. People can simply npm install loom-<name> --save and start using them.

Publishing Template Engines to npm for Everybody

To add support for your favorite templating engine you can either add a file to loom/engines or publish a module to npm named loom-engine-<ext>. Loom will attempt to require the engine if it doesn't find it in your project.

Generator API

Loom has a generic generator that can be overridden to meet your specific use case. Generators can export a few methods that loom will use.

Your generator can implement as many methods as you need, loom will merge in the generic_generator methods that you don't provide.

Here's a generator that does nothing:


exports.before = function(){};
exports.present = function(){};
exports.savePath = function(){};
exports.write = function(){};
exports.render = function(){};
exports.template = '';
// exports.template = function(){};
// exports.templates = [];
// exports.templates = function(){};

Below is documentation on generator API, also, check out the generic generator.

All methods share the first two arguments: next, and env.

  • next - all methods are asynchronous, so when you're done doing what you need to do, call next(val).
  • env - the loom environment, it contains all sorts of information about the generate command the user ran.


Executes before anything else happens. Useful if you need to set or change some things on env before it moves through the other methods of your generator.


function(next, env)

  1. next (Function) - the callback.
  2. env (Object) - the loom environment object.


You're probably going to want env.args and env.params.


function(next, env)


  1. next (Function) - the callback.
  2. env (Object) - the loom environment object.


Lets make a generator that logs the arguments to explore how this works.


exports.present = function(next, env) {

The following are commands followed by what is logged for the arguments:

generate model user name:string age:number
{ args: ['user'], params: { name: 'string', age: 'number' } }
generate model foo bar baz qux:1 quux:2
{ args: ['foo''bar''baz' ]
  params: { qux: '1', quux: '2' } }

As you can see, the space separated values become the args and the key:value pairs are wrapped up into the params argument.


Determines which template to render.

exports.template can simply be a string, or a function if you need to compute it.

Paths are relative to the ./loom/templates directory.


To use a template found at loom/templates/spec/models/model.spec.js.hbs:

exports.template = 'spec/models/model.spec.js.hbs';
exports.template = function(next) {
  // some computation


Unless you override generator.write the generated file will be saved in the mirrored location in loom/templates, so the example above will be saved to spec/models/<name>.spec.js.


Same as template but is an array of template paths that take precendence over template. Each template will receive the same locals returned from present. Can also be a function that calls back an array.


exports.templates = [
exports.templates = function(next) {


Determines the path in which to save a template.


function(next, env, template)


  1. next (Function) - callback with the savePath you want
  2. env (Object) - the loom environment object
  3. template (String) - the path of the template being rendered


Writes a rendered template to the file system, its unlikely you'll want to override this.


function(next, env, savePath, src)


Determines how to render the template, its unlinkely you'll want to override this.


function(next, env, engine, templatePath, locals)


  • conflict resolution when two generators want to save to the same path
  • --force option to overwrite files (better for scripting so you don't get the prompt)

License and Copyright

MIT Style license

(c) 2013 Ryan Florence




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