Localization Sin #1
Never, ever, ever assume you can pluralize something by adding an “s” to the end of it.
Not only does this not remain true in every language, but you will grow lax and start doing silly things like:
var text = "You have " + swordQuantity + " sword" + (1 === swordQuantity ? "" : "s") + ".";
And when you do that once, you’re likely to do it all over the place. Then, instead of simple text replacement during localization, you have to rewrite whole swaths of code to handle how different languages pluralize.
Just a friendly tip.