I'm writing a web app in Node. If I've got some JS file db.js with a function init in it how could I call that function from the command line?
No comment on why you want to do this, or what might be a more standard practice: here is a solution to your question.... Keep in mind that the type of quotes required by your command line may vary.
In your db.js, export the init function. There are many ways, but for example:
module.exports.init = function () {
console.log('hi');
};
Then call it like this, assuming your db.js is in the same directory as your command prompt:
node -e 'require("./db").init()'
If your db.js were a module db.mjs, use a dynamic import to load the module:
node -e 'import("./db.mjs").then( loadedModule => loadedModule.init() )'
To other readers, the OP's init function could have been called anything, it is not important, it is just the specific name used in the question.
Update 2020 - CLI
As #mix3d pointed out you can just run a command where file.js is your file and someFunction is your function optionally followed by parameters separated with spaces
npx run-func file.js someFunction "just some parameter"
That's it.
file.js called in the example above
const someFunction = (param) => console.log('Welcome, your param is', param)
// exporting is crucial
module.exports = { someFunction }
More detailed description
Run directly from CLI (global)
Install
npm i -g run-func
Usage i.e. run function "init", it must be exported, see the bottom
run-func db.js init
or
Run from package.json script (local)
Install
npm i -S run-func
Setup
"scripts": {
"init": "run-func db.js init"
}
Usage
npm run init
Params
Any following arguments will be passed as function parameters init(param1, param2)
run-func db.js init param1 param2
Important
the function (in this example init) must be exported in the file containing it
module.exports = { init };
or ES6 export
export { init };
As per the other answers, add the following to someFile.js
module.exports.someFunction = function () {
console.log('hi');
};
You can then add the following to package.json
"scripts": {
"myScript": "node -e 'require(\"./someFile\").someFunction()'"
}
From the terminal, you can then call
npm run myScript
I find this a much easier way to remember the commands and use them
Try make-runnable.
In db.js, add require('make-runnable'); to the end.
Now you can do:
node db.js init
Any further args would get passed to the init method, in the form of a list or key-value pairs.
Sometimes you want to run a function via CLI, sometimes you want to require it from another module. Here's how to do both.
// file to run
const runMe = () => {}
if (require.main === module) {
runMe()
}
module.exports = runMe
This one is dirty but works :)
I will be calling main() function from my script. Previously I just put calls to main at the end of script. However I did add some other functions and exported them from script (to use functions in some other parts of code) - but I dont want to execute main() function every time I import other functions in other scripts.
So I did this,
in my script i removed call to main(), and instead at the end of script I put this check:
if (process.argv.includes('main')) {
main();
}
So when I want to call that function in CLI: node src/myScript.js main
simple way:
let's say you have db.js file in a helpers directory in project structure.
now go inside helpers directory and go to node console
helpers $ node
2) require db.js file
> var db = require("./db")
3) call your function (in your case its init())
> db.init()
hope this helps
Updated for 2022 - If you've switched to ES Modules, you can't use the require tricks, you'd need to use dynamic imports:
node -e 'import("./db.js").then(dbMod => dbMod.init());'
or with the --experimental-specifier-resolution=node flag:
node --experimental-specifier-resolution=node -e 'import("./db").then(dbMod => dbMod.init());'
If you turn db.js into a module you can require it from db_init.js and just: node db_init.js.
db.js:
module.exports = {
method1: function () { ... },
method2: function () { ... }
}
db_init.js:
var db = require('./db');
db.method1();
db.method2();
I do a IIFE, something like that:
(() => init())();
this code will be executed immediately and invoke the init function.
You can also run TypeScript with ts-node similar to #LeeGoddard answer.
In my case, I wanted to use app and init separately for testing purposes.
// app.ts
export const app = express();
export async function init(): Promise<void> {
// app init logic...
}
npx ts-node -e 'require("./src/app").init();'
npx ts-node -e 'import("./src/app").then(a => a.init());' // esmodule
maybe this method is not what you mean, but who knows it can help
index.js
const arg = process.argv.splice(2);
function printToCli(text){
console.log(text)
}
switch(arg[0]){
case "--run":
printToCli("how are you")
break;
default: console.log("use --run flag");
}
and run command node . --run
command line
probuss-MacBook-Air:fb_v8 probus$ node . --run
how are you
probuss-MacBook-Air:fb_v8 probus$
and you can add more arg[0] , arg[1], arg[2] ... and more
for node . --run -myarg1 -myarg2
If you want to include environment variables from your .env files, you can use env-cmd:
npx env-cmd node -e 'require("./db").init()'
If you want run a specific function in the file too, use run-func:
npx env-cmd npx run-func db.js init someArg
Or, to provide an argument for the accepted answer you'd have to do something like:
npx env-cmd node -e 'require("./db").init(someArg)'
Writing/updating an expression here is less explicit (so easier to miss when you're checking back, for example) than providing different arguments to the commands, so I recommend using env-cmd with run-func.
Note: I also usually add --experimental-modules on the end when necessary.
Inspired by https://github.com/DVLP/run-func/blob/master/index.js
I create https://github.com/JiangWeixian/esrua
if file index.ts
export const welcome = (msg: string) => {
console.log(`hello ${msg}`)
}
just run
esrua ./index.ts welcome -p world
will output hello world
If your file just contains your function, for example:
myFile.js:
function myMethod(someVariable) {
console.log(someVariable)
}
Calling it from the command line like this nothing will happen:
node myFile.js
But if you change your file:
myFile.js:
myMethod("Hello World");
function myMethod(someVariable) {
console.log(someVariable)
}
Now this will work from the command line:
node myFile.js
Related
I'm trying to adapt the game of life tutorial to call user-defined JS (instead of alert) from Rust:
index.js:
import * as wasm from "testing-wasm";
export const jsfunc = () => {
console.log("jsfunc called");
};
// Call Rust from JS. This function will call `jsfunc`, declared above.
wasm.rustfunc();
lib.rs:
mod utils;
use wasm_bindgen::prelude::*;
// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
// allocator.
#[cfg(feature = "wee_alloc")]
#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
#[wasm_bindgen(module = "/www/index.js")]
extern "C" {
fn jsfunc();
}
#[wasm_bindgen]
pub fn rustfunc() {
// call JS
jsfunc();
}
wasm-pack build runs fine. But running the web project (npm run start) can't resolve the import anymore:
ERROR in ../pkg/snippets/testing-wasm-8ea926e8de57779d/www/index.js
Module not found: Error: Can't resolve 'testing-wasm' in '/Users/ischuetz/dev/ct-an/testing-wasm/pkg/snippets/testing-wasm-8ea926e8de57779d/www'
# ../pkg/snippets/testing-wasm-8ea926e8de57779d/www/index.js 1:0-37 7:0-13
# ../pkg/testing_wasm_bg.wasm
# ../pkg/testing_wasm.js
# ./index.js
# ./bootstrap.js
It works before introducing the circular dependency.
Any ideas? I also found import_js in wasm-bindgen but there's no direct call to Rust from JS.
in your Cargo.toml file add this:
[lib]
# if you want to integrate your rust code with javascript we use cdylib
crate-type=["cdylib"]
since you are using wasm-bindgen and wee_alloc and I assume it is already in your .toml file:
[dependencies]
wasm-bindgen="0.2.63"
wee_alloc="0.4.5"
When you build your code, pkg folder is created which includes glue javascript code wasm code. Now you need to get this pkg folder into the node modules. To do so, you have to link it to your javascript project's package.json:
"dependencies": {
// your path to ../pkg might be different
"rust_project": "file:../pkg",
},
Then in your javascript project directory, npm install. You will see that rust_project module is in your node_modules directory.
In your javascript file:
import rustfunc from "rust_project";
Now you can call your function
I have files as represented:
-js/
- calc.js
- tool.js
-index.html
calc.js is a node module of following structure:
module.exports = {
calculate: function() {...},
getPrecision: function() {...}
}
and tool.js use require and adds some functions, like that:
const fpcalc = require('./fpcalc');
function changeState() {
//some code using fpcalc
}
I used Browserify to generate bundle.js and added that as script src.
One of my buttons on HTML page is using onclick=changeState(). After clicking I'm getting
ReferenceError: changeState is not defined
at HTMLAnchorElement.onclick
Why is that? Is there any other way to make it work?
The function "changeState" is not exported in your tool.js.
That means it is only visible inside your bundle.js, but not outside.
Have a look at this: https://makerlog.org/posts/creating-js-library-builds-with-browserify-and-other-npm-modules
It shows you how to expose your code to the global namespace in javascript.
Here's a very simple way to make it work like you want.
const fpcalc = require('./fpcalc');
window.changeState = () => {
//some code using fpcalc
}
I have same error, here is my working example.
mac, browserify https://github.com/perliedman/reproject
Must use sudo install globally
sudo npm install -g brwoserify
https://github.com/perliedman/reproject
sudo npm install reproject // install locally is fine
Must manually create 'dist' folder for later output file use
Must use --s expose global variable function 'reproject' and or 'toWgs84' you will use later in browser js.
Without --s , will get 'reproject' undefined error . https://makerlog.org/posts/creating-js-library-builds-with-browserify-and-other-npm-modules
browserify --help will list all options.
-o means output file directory
browserify node_modules/reproject/index.js --s reproject -o node_modules/reproject/dist/reproject.js
HTML script tag include your above dist/reproject.js
Now, you will not get 'reproejct' undefined error
return reproject(_geometry_, ___from_projection, proj4.WGS84, crss)
I've been using gulp for a while now and know how to import another node module, e.g.
var sass = require('gulp-sass');
That's fine, but my gulpfile is filling up with code that I'd like to move into a separate file and "require". Specifically I am writing a postcss plugin, which I already have working when declared as a function inside of the gulpfile. My question is how to put my function in an external file and require it like I do a node module. Do I need to "export" the function in the file being required? Do I need to use ES6 modules or something like that?
As an aside, I realise that if i was doing this probably I would either (A) turn this into a proper node module and put it on a private NPM repository, but that seems unnecessary, or (B) turn it into a proper gulp plugin, but that would require learning how to author a gulp plugin and learning about streams and stuff. Both of these are probably better but would take more time so I've decided to just keep the function simple and local for now.
First create a new js file (here ./lib/myModule.js):
//./lib/myModule.js
module.exports = {
fn1: function() { /**/ },
fn2: function() { /**/ },
}
You could also pass some arguments to your module:
// ./lib/myAwesomeModule.js
var fn1 = function() {
}
module.exports = function(args) {
fn1: fn1,
fn2: function() {
// do something with the args variable
},
}
Then require it in your gulpfile:
//gulpfile.js
var myModule = require('./lib/myModule')
// Note: here you required and call the function with some parameters
var myAwesomeModule = require('./lib/myAwesomeModule')({
super: "duper",
env: "development"
});
// you could also have done
/*
var myAwesomeModuleRequire = require('./lib/myAwesomeModule')
var myAwesomeModule = myAwesomeModuleRequire({
super: "duper",
env: "development"
});
*/
gulp.task('test', function() {
gulp.src()
.pipe(myModule.fn1)
.pipe(myAwesomeModule.fn1)
.gulp.dest()
}
First, you have to add export default <nameOfYourFile> at the end of your file
Then to use it, write import gulp from 'gulp'
If you have an error message, install babel-core and babel-preset-es2015 with NPM, and add a preset "presets": ["es2015"] in your .babelrc config file.
I fix my problem by install:
npm i babel-plugin-add-module-exports
Then i add "plugins": [["add-module-exports"]] to the .babelrc
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...
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