Example of how the Node.js community prepends commas

node_js_prepended_comma.js

// Consider the humble object:
var dave = {
  name: "Dave",
  age: 39,
  color: "green"
};

// If I add to this and forget to add another trailing comma, it's a
// syntax error:
var dave = {
  name: "Dave",
  age: 39,
  color: "green"
  pants: "none"
};

// Now, since the dark ages of C to the modern era of Ruby and even
// Javascript, compilers have allowed you to leave an extra trailing
// comma for just this problem (and also for simple code emitter
// scripts: for value in values { write a value, write a comma }, etc:
var dave = {
  name: "Dave",
  age: 39,
  color: "green",
  pants: "none",
};
// Try it in Ruby, kids! ray = [1, 2, 3,] # it works!

// But the javascript engine in IE (it's ALWAYS IE, amirite?) chokes
// on that trailing comma. So we're back to accidentally leaving out
// those @#$! commas. The Node.js community has worked around this by
// saying "well, since the comma is apparently the most important
// character on the line, it should LOOK like the most important
// character". (I'm not saying I entirely agree, but I do actually
// understand the sentiment. So here's how the Node guys do it:
var dave = {
  name: "Dave"
  , age: 39
  , color: "green"
  , pants: "none"
};

// Now when you add a new item, you'll never forget the comma because
// you always add the comma on the same line as the new element. Also
// because you CAN'T STOP BARFING and that's a pretty good mnemonic
// trigger.

Technically, the comma is supposed to be aligned such that the words line up.