Develop Reference

How to get Jest to see the functions I am writing for MongoDB Stitch?

I am trying out Stitch, a serverless/hosted JavaScript environment from MongoDB. My main purpose is to help me learn modern JavaScript, but I am trying to write a useful app as well.
I have written the following function, and saved it in my Stitch app. I believe this follows the documented way to write functions in Stitch, and I have tested it from the Stitch administration console:
exports = function(query){
const http = context.services.get("HTTP");
const urlBase = context.values.get("stackOverflowApiUrl");
const options = [
'order=desc',
'sort=activity',
'site=stackoverflow',
'q=' + encodeURIComponent(query),
'user=472495',
'filter=!--uPQ.wqQ0zW'
];
return http
.get({ url: urlBase + '?' + options.join('&') })
.then(response => {
// The response body is encoded as raw BSON.Binary. Parse it to JSON.
const ejson_body = EJSON.parse(response.body.text());
return ejson_body.total;
});
};
This code is pretty simple - it obtains an http object for making external API fetches, and obtains a configuration value for a URL urlBase to contact (resolving to https://api.stackexchange.com/2.2/search/excerpts) and then makes a call to the Stack Overflow Data API. This runs a search query against my user and returns the number of results.
So far so good. Now, I want to call this function locally, in Jest. To do this, I have installed Node and Jest in a local Docker container, and have written the following test function:
const callApi = require('./source');
test('Simple fetch with no user', () => {
expect(callApi('hello')).toBe(123);
});
This fails, with the following error:
~ # jest
FAIL functions/callApi/source.test.js
✕ Simple fetch with no user (3ms)
● Simple fetch with no user
TypeError: callApi is not a function
2 |
3 | test('Simple fetch with no user', () => {
> 4 | expect(callApi('hello')).toBe(123);
| ^
5 | });
6 |
at Object.<anonymous>.test (functions/callApi/source.test.js:4:12)
Test Suites: 1 failed, 1 total
Tests: 1 failed, 1 total
Snapshots: 0 total
Time: 1.418s
Ran all test suites.
(In fact I was expecting it to fail, since it contains a global object context that Jest does not have access to. I will work out how to mock that later, but for now Jest cannot even see the function at all).
I suspect I can see the reason - in the Jest introduction docs, one has to do this for the SUT:
module.exports = function() { ... }
However the Stitch docs seem to require functions to be defined as:
exports = function() { ... }
I do not have a background in JavaScript to understand the difference. I could try module.exports in Stitch, but I would rather not, since this would either not work now, or cause a breakage in the future. Can Jest be instructed to "see" bare exports without the module prefix?
Incidentally, I have picked Jest because it is popular, and because some of my JavaScript colleagues vouch for it. However, I am not wedded to it, and would be happy to use something else if it is known to be better for Stitch development.
Update
Following the useful answer from jperl below, I find that the following construction is not possible in Stitch:
module.exports = exports = function() {}
I also cannot do this:
exports = function() {}
module.exports = exports
If I try either, I get the following error:
runtime error during function validation
So it looks like I have to get Jest to work without module.exports, or create a glue file that imports the exports version into module.exports, with the main file being used by Stitch, and the glue importer being used by Jest.

I suggest you to read this thread. And you're right in thinking it has to do with modules.exports vs exports. The thing is that module.exports and exports first point to the same thing. So something like this works:
//modify the same object that modules.exports is pointing to
exports.a = {}
exports.b = {}
but this won't:
exports = {}
Why? Because now exports points to something else than module.exports so what you're doing has no effect at all.
Update
Following some updates in the comments, we came to the view that Stitch does not seem to support the export format that Jest requires.

This is an addendum to jperl's answer, to show how I got Jest working while respecting Stitch's limitations.
Firstly, it is worth noting how a Stitch application is laid out. This is determined by the import/export format.
auth_providers/
functions/
function_name_1/
config.json
source.js
function_name_2/
config.json
source.js
...
services/
values/
The config.json file is created by Stitch remotely, and is obtained through a export. This contains ID information to uniquely identify the function in the same folder.
I believe it is common JavaScript practice to mix tests with source code, so I am following that style (I am new to modern JS, and I confess I find this style untidy, but I am running with it nevertheless). Thus I add a source.test.js file in each function folder.
Finally, since there is a discrepancy between what Stitch requires and what Jest requires, I have written a script to create a source code file under _source.js in each function folder.
So, each folder will contain these files (the underscore files will probably be ignored by Git, as they will always be generated):
_source.js
config.json
source.js
source.test.js
In order to create the underscored copies, I am using this shell script:
#!/bin/bash
# Copy all source.js files as _source.js
for f in $(find functions/ -name source.js); do cp -- "$f" "$(dirname $f)/_$(basename $f)"; done
# Search and replace in all _source.js files
for f in $(find functions/ -name _source.js); do sed -i -e 's/exports =/module.exports =/g' $f; done
A bit hacky perhaps, but it works!

How to get Jenkins BUILD_NUMBER in JavaScript using GULP/NODE?

I have a gulp task getBuildNumber which uses Child Process to execute the script.
gulp.task('getBuildNumber', function() {
var buildNumber = child_process.execSync("echo $BUILD_NUMBER").toString().trim();
console.log(buildNumber);
});
When I run the following command for gulp
npm run gulp -- getBuildNumber
I always get the output as $BUILD_NUMBER and not the actual Jenkins build number.
Can someone please suggest on how to proceed with this?

You can access environment variables with process.env.
For example:
console.log(process.env.BUILD_NUMBER);

According to https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback, you need to escape special characters:
exec('echo "The \\$HOME variable is $HOME"');
In your case, this means you'd need to use
[...]child_process.execSync("echo \\$BUILD_NUMBER").toString().trim();[...]
^^

Hide 'Running X task' in grunt

I have been working on a project setup and deploy Gruntfile but would like to hide the command line output so that the following:
Running "init" task
Running "prompt:init" (prompt) task
[?] If you continue your project information will be overwritten.
Continue? (Y/n)
becomes
[?] If you continue your project information will be overwritten.
Continue? (Y/n)
when running grunt. I know it's only cosmetic but it's something I would like to do and cannot seem to find anything on Grunt's API documentation to indicate this can be done.

This is currently not supported, but possible thanks to the following workaround (from shama on GitHub):
grunt.log.header = function () {};
Basically, this overrides the log header function (which is responsible for the "running x task" message) by an empty function that does nothing, and more importantly, outputs nothing.
There's another way to do it:
First, run npm install grunt-log-headers to install grunt-log-headers.
Then add require('grunt-log-headers')(grunt); to your Gruntfile.js to enable it.
Finally, add this to any task for which you want to hide the log header:
options: {
gruntLogHeader: false
}
Example:
grunt.initConfig({
sometask: {
options: {
gruntLogHeader: false,
}
}
});
In fact, an issue has already been created for this. It's currently being worked on, and will normally be available in the version 0.5.0.

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:
NODE_PATH=. node -r myscript.js
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

First I tried
$ node --interactive foo.js
but it just runs foo.js, with no REPL.
If you're using export and import in your js, run npm init -y, then tell node that you're using modules with the "type": "module", line -
{
"name": "neomem",
"version": "1.0.0",
"description": "",
"type": "module",
"main": "home.js",
"keywords": [],
"author": "",
"license": "ISC"
}
Then you can run node and import a file with dynamic import -
$ node
Welcome to Node.js v18.1.0.
Type ".help" for more information.
> home = await import('./home.js')
[Module: null prototype] {
get: [AsyncFunction: get],
start: [AsyncFunction: start]
}
> home.get('hello')
Kind of a roundabout way of doing it - having a command line switch would be nice...

How do I load my script into the node.js REPL?

I have a script foo.js that contains some functions I want to play with in the REPL.
Is there a way to have node execute my script and then jump into a REPL with all the declared globals, like I can with python -i foo.py or ghci foo.hs?

There is still nothing built-in to provide the exact functionality you describe. However, an alternative to using require it to use the .load command within the REPL, like such:
.load foo.js
It loads the file in line by line just as if you had typed it in the REPL. Unlike require this pollutes the REPL history with the commands you loaded. However, it has the advantage of being repeatable because it is not cached like require.
Which is better for you will depend on your use case.
Edit: It has limited applicability because it does not work in strict mode, but three years later I have learned that if your script does not have 'use strict', you can use eval to load your script without polluting the REPL history:
var fs = require('fs');
eval(fs.readFileSync('foo.js').toString())

i always use this command
node -i -e "$(< yourScript.js)"
works exactly as in Python without any packages.

I made Vorpal.js, which handles this problem by turning your node add into an interactive CLI. It supports a REPL extension, which drops you into a REPL within the context of your running app.
var vorpal = require('vorpal')();
var repl = require('vorpal-repl');
vorpal
.delimiter('myapp>')
.use(repl)
.show()
.parse(process.argv);
Then you can run the app and it will drop into a REPL.
$ node myapp.js repl
myapp> repl:

Another way is to define those functions as global.
global.helloWorld = function() { console.log("Hello World"); }
Then preload the file in the REPL as:
node -r ./file.js
Then the function helloWorld can be accessed directly in the REPL.

Here's a bash function version of
George's answer:
noderepl() {
FILE_CONTENTS="$(< $1 )"
node -i -e "$FILE_CONTENTS"
}
If you put this in your ~/.bash_profile you can use it like an alias, i.e.:
noderepl foo.js

I created replpad since I got tired of reloading the script repeatedly.
Simply install it via: npm install -g replpad
Then use it by running: replpad
If you want it to watch all files in the current and all subdirectories and pipe them into the repl when they change do: replpad .
Check out the videos on the site to get a better idea of how it works and learn about some other nice features that it has like these:
access core module docs in the repl via the dox() function that is added to every core function, i.e. fs.readdir.dox()
access user module readmes in the repl via the dox() function that is added to every module installed via npm,
i.e. marked.dox()
access function's highlighted source code, info on where function was defined (file, linenumber) and function
comments and/or jsdocs where possible via the src property that is added to every function, i.e. express.logger.src
scriptie-talkie support (see .talk command)
adds commands and keyboard shortcuts
vim key bindings
key map support
parens matching via match token plugin
appends code entered in repl back to file via keyboard shortcut or .append command
See: https://github.com/thlorenz/replpad

Why not load the file into an interactive node repl?
node -h
-e, --eval script evaluate script
-i, --interactive always enter the REPL even if stdin
node -e 'var client = require("./build/main/index.js"); console.log("Use `client` in repl")' -i
Then you can add to package.json scripts
"repl": "node -e 'var client = require(\"./build/main/index.js\"); console.log(\"Use `client` in repl\")' -i",
tested using node v8.1.2

Currently you can't do that directly, but you can mylib = require('./foo.js') in the REPL. Remember methods are exported, not declared as globals.

replpad is cool, but for a quick and easy way to load a file into node, import its variables and start a repl, you can add the following code to the end of your .js file
if (require.main === module){
(function() {
var _context = require('repl').start({prompt: '$> '}).context;
var scope = require('lexical-scope')(require('fs').readFileSync(__filename));
for (var name in scope.locals[''] )
_context[scope.locals[''][name]] = eval(scope.locals[''][name]);
for (name in scope.globals.exported)
_context[scope.globals.exported[name]] = eval(scope.globals.exported[name]);
})();
}
Now if your file is src.js, running node src.js will start node, load the file, start a REPL, and copy all the objects declared as var at the top level as well as any exported globals.
The if (require.main === module) ensures that this code will not be executed if src.js is included through a require statement. I fact, you can add any code you want to be excuted when you are running src.js standalone for debugging purposes inside the if statement.

Another suggestion that I do not see here: try this little bit of code
#!/usr/bin/env node
'use strict';
const repl = require('repl');
const cli = repl.start({ replMode: repl.REPL_MODE_STRICT });
cli.context.foo = require('./foo'); // injects it into the repl
Then you can simply run this script and it will include foo as a variable

Old answer
type test.js|node -i
Will open the node REPL and type in all lines from test.js into REPL, but for some reason node will quit after file ends
Another problem is, that functions will not be hoisted.
Better answer
node -e require('repl').start({useGlobal:true}); -r ./test2.js
Then all globals declared without var within test2.js will be available in the REPL
not sure why var a in global scope will not be available

There is an Official Node.js REPL that supports also async methods
console.js
const repl = require('repl')
const mongoose = require('mongoose')
const run = async () => {
await mongoose.connect(process.env.DB_URL, {
useNewUrlParser: true,
useUnifiedTopology: true
})
const r = repl.start(`(${process.env.NODE_EN}) ⚡️ `)
r.context.User = require('./src/models/user.model')
r.context.mongoose = mongoose
console.log(`Ready 🚀`);
}
run()
Start the console:
NODE_OPTIONS=--experimental-repl-await node console.js
User model its exposed to console
await User.find({})
source