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JavaScript Express Basics (2015) Getting Started with Express Improving your first app, some final touches

Vincent Wang
Vincent Wang
1,976 Points
Posted by Vincent Wang
Vincent Wang
1,976 Points

var app = express();

What does this line do in particular?

I am confused because I thought we have already required the express package, so why can't we call express.listen(3000) instead of having to call another method express() for this - what does this method do specifically?

1 Answer

Aaron Price
Aaron Price
5,974 Points
Aaron Price
Aaron Price
5,974 Points 
express()

is a function that returns an object. if you did express.listen(3000) it wouldn't work because the function itself doesn't have a .listen method.

But even if you tried to do this

express().set(/* ... */)
express().use(/* ... */)
express().listen(3000)

it wouldn't work because you would be creating three separate objects, which each would only be self-aware and couldn't use the middleware or values you passed to the other 2.