simplicity

Practice 26

Dangle That Comma

Talking about lists of things, here’s a tip that can lead to some pretty serious arguments.

When you write a list of things, you separate each element with a delimiter character (often a comma):

[ 1, 2, 3 ]

Some languages (C, C#, C++, JavaScript, Python, and Ruby, to name a few) allow a delimiter after the last element of a list:

[ 1, 2, 3, ]     # still just three elements

Why does that little comma help make code easy to change? Let’s imagine a list of the five largest lakes, ordered by size, starting with the largest:

BIG_LAKES = [
  "Caspian",
  "Superior",
  "Victoria",
  "Huron",
  "Michigan"
]

The customer changes their mind and wants the list in alphabetic order. No problem—you use your editor’s ...