javascript - npm start vs node app.js

Question

I'm extremely new to Node and trying to get my head around app basics. I'm curious as to why these two commands:

node app.js

--vs--

npm start

output the same thing to the console and appear to continue "listening", but why when I try to access http://localhost:3000 I get a 404 only when running the first command.

I see that Express 4 seems to have a different app structure, but why is it that one successfully listens and the other doesn't, despite the same behavior in the console?

Any explanation is helpful. Thanks!

Answer 1

The two of these commands aren't necessarily the same. npm start runs whatever the 'start' script config says to run as defined in your 'package.json', node app.js executes the 'app.js' file in 'node'. See http://browsenpm.org/package.json for more info. So if you had the following package.json then the commands are completely different.

{
    "name": "my cool node project",
    ....
    "scripts": {
        "start": "node index.js"
    }
    ....
}

The following package.json is what you'll want to make them identical.

{
    "name": "my cool node project",
    ....
    "scripts": {
        "start": "node app.js"
    }
    ....
}

I'd start by checking what the 'start' script is set to run and try running the same command directly in your CLI rather than through NPM to see where the difference is.

but why is it that one successfully listens and the other doesn't

If the server is returning a 404 this would suggest the server is listening, but either the document root or access permissions aren't being setup properly so it returns a 'File not Found' response.