Learning CoffeeScript (with a dash of Node.js)

This post is part of my weekly tech learning series, where I take one hour each week to try out a piece of technology that I'd like to learn.

Today I decided to start my tech learning with CoffeeScript. CoffeeScript is "a little language that compiles into JavaScript" and has been really popular over the past year.

I know a good amount of JavaScript and have written a few JavaScript applications over the past few months so I was ready to see what improvements CoffeeScript includes.

Installing CoffeeScript was easy since I just used version 1.2.0 which is included in Ubuntu. It uses node which is surprising, I thought it was a RubyGem.

Todo App

For this session I decided to build a simple todo list. I have experience with them and it's a small enough application that I can try in later weeks.

Right off the bat the syntax was different, not better or worse than JavaScript but different. I think it might be a little better after some heavy usage due to it's sparseness (e.g. removing function(), curly braces, and semi-colons).


Once I got into CoffeeScript, I quickly got into a flow.

  1. I had my coffee file open in one window,
  2. the CoffeeScript compiler in the background running --watch to rebuild my code,
  3. and a console open with node to run my compiled JavaScript.

It wasn't quite a REPL nor was it TDD but I was able to cycle between code/build/test quickly. I ended up with a basic TodoList class that let you add, remove, count, and summarize your list of todos. Nothing fancy.

Node.js Problems

The biggest problem I ran into was with node.js. Since I didn't want to load everything into a browser I tried to build a small JavaScript program that would run in node. Since I was writing my application code in a separate file, getting it imported into node was a huge pain (eval helped). I know I was doing something wrong, hopefully I can figure out the right way when I spend some time learning node.js later.


Overall I was happy with CoffeeScript. With a little bit of regular usage I should be just as productive as with JavaScript. I can see it being especially useful when needing to model things more into classes.


# todo.coffee class TodoList constructor: -> @items = []

add: (todoItem) -> @items.push(todoItem)

remove: (todoItem) -> @items = _.reject @items, (existingTodo) -> existingTodo == todoItem

count: -> @items.length

summary: -> this.puts("==================================================") this.puts("= You have #{ this.count() } todo items") for todo in @items this.puts(todo) this.puts("--------------------------------------------------")

puts: (line) -> console.log(line)

# app.coffee

Node app

global._ = require("../vendor/underscore-min.js")

Hackery to get node to load todo.js in scope

eval(require('fs').readFileSync('lib/todo.js', 'utf8'));

Working on todo list

list = new TodoList() list.add("Install CoffeeScript") list.add("Install Node") list.add("Install coffee-mode") list.remove("Install CoffeeScript")


Compiled output:

var TodoList;

TodoList = (function() {

function TodoList() { this.items = []; }

TodoList.prototype.add = function(todoItem) { return this.items.push(todoItem); };

TodoList.prototype.remove = function(todoItem) { return this.items = _.reject(this.items, function(existingTodo) { return existingTodo === todoItem; }); };

TodoList.prototype.count = function() { return this.items.length; };

TodoList.prototype.summary = function() { var todo, _i, _len, _ref; this.puts("=================================================="); this.puts("= You have " + (this.count()) + " todo items"); _ref = this.items; for (_i = 0, _len = _ref.length; _i < _len; _i++) { todo = _ref[_i]; this.puts(todo); } return this.puts("--------------------------------------------------"); };

TodoList.prototype.puts = function(line) { return console.log(line); };

return TodoList;


var list;

global._ = require("../vendor/underscore-min.js");

eval(require('fs').readFileSync('lib/todo.js', 'utf8'));

list = new TodoList();

list.add("Install CoffeeScript");

list.add("Install Node");

list.add("Install coffee-mode");

list.remove("Install CoffeeScript");


Topics: Coffeescript javascript Node js Tech learning

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