execute some code and then go into interactive node

Is there a way to execute some code (in a file or from a string, doesn't really matter) before dropping into interactive mode in node.js?

For example, if I create a script __preamble__.js which contains:

console.log("preamble executed! poor guy!");

and a user types node __preamble__.js they get this output:

preamble executed! poor guy!
> [interactive mode]

Really old question but...

I was looking for something similar, I believe, and found out this. You can open the REPL (typing node on your terminal) and then load a file. Like this: .load ./script.js. Press enter and the file content will be executed. Now everything created (object, variable, function) in your script will be available.

For example:

// script.js
var y = {
    name: 'obj',
    status: true
};

var x = setInterval(function () {
    console.log('As time goes by...');
}, 5000);

On the REPL:

//REPL
.load ./script.js

Now you type on the REPL and interact with the "living code". You can console.log(y) or clearInterval(x);

It will be a bit odd, cause "As time goes by..." keep showing up every five seconds (or so). But it will work!

You can start a new repl in your Node software pretty easily:

var repl = require("repl");
var r = repl.start("node> ");
r.context.pause = pauseHTTP;
r.context.resume = resumeHTTP;

From within the REPL you can then call pause() or resume() and execute the functions pauseHTTP() and resumeHTTP() directly. Just assign whatever you want to expose to the REPL's context member.

This can be achieved with the current version of NodeJS (5.9.1):

$ node -i -e "console.log('A message')"

The -e flag evaluates the string and the -i flag begins the interactive mode.

You can read more in the referenced pull request

node -r allows you to require a module when REPL starts up. NODE_PATH sets the module search path. So you can run something like this on your command line:

This should put you in a REPL with your script loaded.

I've recently started a project to create an advanced interactive shell for Node and associated languages like CoffeeScript. One of the features is loading a file or string in the context of the interpreter at startup which takes into account the loaded language.

http://danielgtaylor.github.com/nesh/

Examples:

# Load a string (Javascript)
nesh -e 'var hello = function (name) { return "Hello, " + name; };'

# Load a string (CoffeeScript)
nesh -c -e 'hello = (name) -> "Hello, #{name}"'

# Load a file (Javascript)
nesh -e hello.js

# Load a file (CoffeeScript)
nesh -c -e hello.coffee

Then in the interpreter you can access the hello function.

Edit: Ignore this. @jaywalking101's answer is much better. Do that instead.

If you're running from inside a Bash shell (Linux, OS X, Cygwin), then

cat __preamble__.js - | node -i

will work. This also spews lots of noise from evaluating each line of preamble.js, but afterwords you land in an interactive shell in the context you want.

(The '-' to 'cat' just specifies "use standard input".)

Similar answer to @slacktracer, but if you are fine using global in your script, you can simply require it instead of (learning and) using .load.

Example lib.js:

global.x = 123;

Example node session:

$ node
> require('./lib')
{}
> x
123

As a nice side-effect, you don't even have to do the var x = require('x'); 0 dance, as module.exports remains an empty object and thus the require result will not fill up your screen with the module's content.

Vorpal.js was built to do just this. It provides an API for building an interactive CLI in the context of your application.

It includes plugins, and one of these is Vorpal-REPL. This lets you type repl and this will drop you into a REPL within the context of your application.

Example to implement:

var vorpal = require('vorpal')();
var repl = require('vorpal-repl');
vorpal.use(repl).show();

// Now you do your custom code...

// If you want to automatically jump
// into REPl mode, just do this:
vorpal.exec('repl');

That's all!

Disclaimer: I wrote Vorpal.

There isn't a way do this natively. You can either enter the node interactive shell node or run a script you have node myScrpt.js. @sarnold is right, in that if you want that for your app, you will need to make it yourself, and using the repl toolkit is helpful for that kind of thing

nit-tool lets you load a node module into the repl interactive and have access to inner module environment (join context) for development purposes

npm install nit-tool -g