Bracket and dot notation in compiled CoffeeScript

Question

I have this piece of code in a Node/Express app:

app.use "/static", express.directory("#{__dirname}/public")
app.use "/static", express.static("#{__dirname}/public")

It compiles to this:

app.use("/static", express.directory("" + __dirname + "/public"));
app.use("/static", express["static"]("" + __dirname + "/public"));

By curiosity, I am wondering: why is the dot notation used for the first call and the bracket notation for the second call?

Answer 1

Because static is reserved in ES3. (not anymore in ES5).

Answer 2

Because static is a reserved word in Javascript prior to EcmaScript 5 .

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Reserved_Words

Some browsers might throw an error if it is used as an object property with the object.word syntax .

object['word'] ensure no error will be thrown.

Answer 3

static is a reserved word (reserved for future use as a keyword) in javascript.

You can see a list of reserved words here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Reserved_Words

For example, x.in compiles to x["in"] , because in is also a reserved word.