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In my package.json I have these two scripts:

  "scripts": {
    "start-watch": "nodemon run-babel index.js",
    "wp-server": "webpack-dev-server",
  }

I have to run these 2 scripts in parallel everytime I start developing in Node.js. The first thing I thought of was adding a third script like this:

"dev": "npm run start-watch && npm run wp-server"

... but that will wait for start-watch to finish before running wp-server.

How can I run these in parallel? Please keep in mind that I need to see the output of these commands. Also, if your solution involves a build tool, I'd rather use gulp instead of grunt because I already use it in another project.

In my package.json I have these two scripts:

  "scripts": {
    "start-watch": "nodemon run-babel index.js",
    "wp-server": "webpack-dev-server",
  }

I have to run these 2 scripts in parallel everytime I start developing in Node.js. The first thing I thought of was adding a third script like this:

"dev": "npm run start-watch && npm run wp-server"

... but that will wait for start-watch to finish before running wp-server.

How can I run these in parallel? Please keep in mind that I need to see the output of these commands. Also, if your solution involves a build tool, I'd rather use gulp instead of grunt because I already use it in another project.

• javascript
• node.js
• build

Share Improve this question Follow edited Nov 27, 2017 at 20:59 E_net4 30k1313 gold badges111111 silver badges151151 bronze badges asked Jun 20, 2015 at 3:42 Andre PenaAndre Pena 59.3k5353 gold badges208208 silver badges257257 bronze badges 7

• 239 && will run your scripts sequentially while & will run them in parallel. – vsync Commented May 30, 2019 at 8:22
• 10 A quick way of doing it is npm run start-watch & npm run wp-server. This will run the first command as a background thread. This works really well when one of the commands is not long running and does not need to be manually exited later. Something like concurrently allows you to kill all the threads at the same time with CTRL-C. – Joshua Pinter Commented Nov 8, 2019 at 18:59
• 6 @vsync Does that apply to Windows? – Clonkex Commented Feb 9, 2021 at 3:31
• 5 @vsync Are you sure? Other comments are saying that's not how it works, and it didn't work in practice for me. – Clonkex Commented Feb 9, 2021 at 23:10
• 6 @Clonkex, yes BUT it's unreliable and I use concurrently npm package instead, which works well, and I only use Windows – vsync Commented Feb 11, 2021 at 9:26

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32 Answers 32

Sorted by: Reset to default 1 2 Next 1051

Use a package called concurrently.

npm i concurrently --save-dev

Then setup your npm run dev task as so:

"dev": "concurrently --kill-others \"npm run start-watch\" \"npm run wp-server\""

If you're using an UNIX-like environment, just use & as the separator:

"dev": "npm run start-watch & npm run wp-server"

Otherwise if you're interested on a cross-platform solution, you could use npm-run-all module:

"dev": "npm-run-all --parallel start-watch wp-server"

From windows cmd you can use start:

"dev": "start npm run start-watch && start npm run wp-server"

Every command launched this way starts in its own window.

You should use npm-run-all (or concurrently, parallelshell), because it has more control over starting and killing commands. The operators &, | are bad ideas because you'll need to manually stop it after all tests are finished.

This is an example for protractor testing through npm:

scripts: {
  "webdriver-start": "./node_modules/protractor/bin/webdriver-manager update && ./node_modules/protractor/bin/webdriver-manager start",
  "protractor": "./node_modules/protractor/bin/protractor ./tests/protractor.conf.js",
  "http-server": "./node_modules/http-server/bin/http-server -a localhost -p 8000",
  "test": "npm-run-all -p -r webdriver-start http-server protractor"
}

-p = Run commands in parallel.

-r = Kill all commands when one of them finishes with an exit code of zero.

Running npm run test will start Selenium driver, start http server (to serve you files) and run protractor tests. Once all tests are finished, it will close the http server and the selenium driver.

I've checked almost all solutions from above and only with npm-run-all I was able to solve all problems. Main advantage over all other solution is an ability to run script with arguments.

{
  "test:static-server": "cross-env NODE_ENV=test node server/testsServer.js",
  "test:jest": "cross-env NODE_ENV=test jest",
  "test": "run-p test:static-server \"test:jest -- {*}\" --",
  "test:coverage": "npm run test -- --coverage",
  "test:watch": "npm run test -- --watchAll",
}

Note run-p is shortcut for npm-run-all --parallel

This allows me to run command with arguments like npm run test:watch -- Something.

EDIT:

There is one more useful option for npm-run-all:

 -r, --race   - - - - - - - Set the flag to kill all tasks when a task
                            finished with zero. This option is valid only
                            with 'parallel' option.

Add -r to your npm-run-all script to kill all processes when one finished with code 0. This is especially useful when you run a HTTP server and another script that use the server.

  "test": "run-p -r test:static-server \"test:jest -- {*}\" --",

I have a crossplatform solution without any additional modules. I was looking for something like a try catch block I could use both in the cmd.exe and in the bash.

The solution is command1 || command2 which seems to work in both enviroments same. So the solution for the OP is:

"scripts": {
  "start-watch": "nodemon run-babel index.js",
  "wp-server": "webpack-dev-server",
  // first command is for the cmd.exe, second one is for the bash
  "dev": "(start npm run start-watch && start npm run wp-server) || (npm run start-watch & npm run wp-server)",
  "start": "npm run dev"
}

Then simple npm start (and npm run dev) will work on all platforms!

Use concurrently to run the commands in parallel with a shared output stream. To make it easy to tell which output is from which process, use the shortened command form, such as npm:wp-server. This causes concurrently to prefix each output line with its command name.

In package.json, your scripts section will look like this:

 "scripts": {
    "start": "concurrently \"npm:start-watch\" \"npm:wp-server\"",
    "start-watch": "nodemon run-babel index.js",
    "wp-server": "webpack-dev-server"
  }

If you replace the double ampersand with a single ampersand, the scripts will run concurrently.

How about forking

Another option to run multiple Node scripts is with a single Node script, which can fork many others. Forking is supported natively in Node, so it adds no dependencies and is cross-platform.

---

Minimal example

This would just run the scripts as-is and assume they're located in the parent script's directory.

// fork-minimal.js - run with: node fork-minimal.js

const childProcess = require('child_process');

let scripts = ['some-script.js', 'some-other-script.js'];
scripts.forEach(script => childProcess.fork(script));

---

Verbose example

This would run the scripts with arguments and configured by the many available options.

// fork-verbose.js - run with: node fork-verbose.js

const childProcess = require('child_process');

let scripts = [
    {
        path: 'some-script.js',
        args: ['-some_arg', '/some_other_arg'],
        options: {cwd: './', env: {NODE_ENV: 'development'}}
    },    
    {
        path: 'some-other-script.js',
        args: ['-another_arg', '/yet_other_arg'],
        options: {cwd: '/some/where/else', env: {NODE_ENV: 'development'}}
    }
];

let runningScripts= [];

scripts.forEach(script => {
    let runningScript = childProcess.fork(script.path, script.args, script.options);

   // Optionally attach event listeners to the script
   runningScript.on('close', () => console.log('Time to die...'))

    runningScripts.push(runningScript); // Keep a reference to the script for later use
});

---

Communicating with forked scripts

Forking also has the added benefit that the parent script can receive events from the forked child processes as well as send back. A common example is for the parent script to kill its forked children.

 runningScripts.forEach(runningScript => runningScript.kill());

For more available events and methods see the ChildProcess documentation

with installing npm install concurrently

"scripts": {
    "start:build": "tsc -w",
    "start:run": "nodemon build/index.js",
    "start": "concurrently  npm:start:*"
  },

npm-run-all --parallel task1 task2

edit:

You need to have npm-run-all installed beforehand. Also check this page for other usage scenarios.

Quick Solution

In this case, I'd say the best bet If this script is for a private module intended to run only on *nix-based machines, you can use the control operator for forking processes, which looks like this: &

An example of doing this in a partial package.json file:

{
  "name": "npm-scripts-forking-example",
  "scripts": {
    "bundle": "watchify -vd -p browserify-hmr index.js -o bundle.js",
    "serve":  "http-server -c 1 -a localhost",
    "serve-bundle": "npm run bundle & npm run serve &"
  }

You'd then execute them both in parallel via npm run serve-bundle. You can enhance the scripts to output the pids of the forked process to a file like so:

"serve-bundle": "npm run bundle & echo \"$!\" > build/bundle.pid && npm run serve & echo \"$!\" > build/serve.pid && npm run open-browser",

Google something like bash control operator for forking to learn more on how it works. I've also provided some further context regarding leveraging Unix techniques in Node projects below:

Further Context RE: Unix Tools & Node.js

If you're not on Windows, Unix tools/techniques often work well to achieve something with Node scripts because:

1. Much of Node.js lovingly imitates Unix principles
2. You're on *nix (incl. OS X) and NPM is using a shell anyway

Modules for system tasks in Nodeland are also often abstractions or approximations of Unix tools, from fs to streams.

There are many ways but the most common 2 ways are here

1. by command

    "scripts": {
        "start": "react-scripts start",
        "dev": "(cd server && npm run start) & npm run start"
      }

2. by npm package

• concurrently npm
• npm-run-all npm (abandoned)
• npm-run-all2 npm (maintenance fork of the above)

step by step guide to run multiple parallel scripts with npm. install npm-run-all package globally

npm i -g npm-run-all

Now install and save this package within project where your package.json exists

npm i npm-run-all --save-dev

Now modify scripts in package.json file this way

"scripts": {
    "server": "live-server index.html",
    "watch": "node-sass scss/style.scss --watch",
    "all": "npm-run-all --parallel server watch"
},

now run this command

npm run all

more detail about this package in given link npm-run-all

My solution is similar to Piittis', though I had some problems using Windows. So I had to validate for win32.

const { spawn } = require("child_process");

function logData(data) {
    console.info(`stdout: ${data}`);
}

function runProcess(target) {
    let command = "npm";
    if (process.platform === "win32") {
        command = "npm.cmd"; // I shit you not
    }
    const myProcess = spawn(command, ["run", target]); // npm run server

    myProcess.stdout.on("data", logData);
    myProcess.stderr.on("data", logData);
}

(() => {
    runProcess("server"); // package json script
    runProcess("client");
})();

npm install npm-run-all --save-dev

package.json:

"scripts": {
  "start-watch": "...",
  "wp-server": "...",
  "dev": "npm-run-all --parallel start-watch wp-server"
}

More info: https://github.com/mysticatea/npm-run-all/blob/master/docs/npm-run-all.md

In a package.json in the parent folder:

"dev": "(cd api && start npm run start) & (cd ../client && start npm run start)"

this work in windows

Just add this npm script to the package.json file in the root folder.

{
  ...
  "scripts": {
    ...
    "start": "react-scripts start", // or whatever else depends on your project
    "dev": "(cd server && npm run start) & (cd ../client && npm run start)"
  }
}

... but that will wait for start-watch to finish before running wp-server.

For that to work, you will have to use start on your command. Others have already illustrated but this is how it will work, your code below:

"dev": "npm run start-watch && npm run wp-server"

Should be :

"dev": " start npm run start-watch && start npm run wp-server"

What this will do is, it will open a separate instance for each command and process them concurrently, which shouldn't be an issue as far as your initial issue is concerned. Why do I say so? It's because these instances both open automatically while you run only 1 statement, which is your initial goal.

How about a good old fashioned Makefile?

This allows you a lot of control including how you manage subshells, dependencies between scripts etc.

# run both scripts
start: server client

# start server and use & to background it
server:
    npm run serve &

# start the client
client:
    npm start

call this Makefile and then you can just type

make start to start everything up. Because the server command is actually running in a child process of the start command when you ctrl-C the server command will also stop - unlike if you just backgrounded it yourself at the shell. Make also gives you command line completion, at least on the shell i'm using. Bonus - the first command will always run so you can actually just type make on it's own here.

I always throw a makefile into my projects, just so I can quickly scan later all the common commands and parameters for each project as I flip between them.

I ran into problems with & and |, which exit statuses and error throwing, respectively.

Other solutions want to run any task with a given name, like npm-run-all, which wasn't my use case.

So I created npm-run-parallel that runs npm scripts asynchronously and reports back when they're done.

So, for your scripts, it'd be:

npm-run-parallel wp-server start-watch

I have been using npm-run-all for some time, but I never got along with it, because the output of the command in watch mode doesn't work well together. For example, if I start create-react-app and jest in watch mode, I will only be able to see the output from the last command I ran. So most of the time, I was running all my commands manually...

This is why, I implement my own lib, run-screen. It still very young project (from yesterday :p ) but it might be worth to look at it, in your case it would be:

run-screen "npm run start-watch" "npm run wp-server"

Then you press the numeric key 1 to see the output of wp-server and press 0 to see the output of start-watch.

This worked for me

{
"start-express": "tsc && nodemon dist/server/server.js",
"start-react": "react-scripts start",
"start-both": "npm -p -r run start-react && -p -r npm run start-express"
}

Both client and server are written in typescript.

The React app is created with create-react-app with the typescript template and is in the default src directory.

Express is in the server directory and the entry file is server.js

typescript code and transpiled into js and is put in the dist directory .

checkout my project for more info: https://github.com/nickjohngray/staticbackeditor

UPDATE: calling npm run dev, to start things off

{"server": "tsc-watch --onSuccess \"node ./dist/server/index.js\"",
"start-server-dev": "npm run build-server-dev && node src/server/index.js",
"client": "webpack-dev-server --mode development --devtool inline-source-map --hot",
"dev": "concurrently \"npm run build-server-dev\"  \"npm run server\" \"npm run client\""}

You can also use pre and post as prefixes on your specific script.

  "scripts": {
    "predev": "nodemon run-babel index.js &",
    "dev": "webpack-dev-server"
  }

And then run: npm run dev

I think the best way is to use npm-run-all as below:

1- npm install -g npm-run-all <--- will be installed globally
2- npm-run-all --parallel server client

In my case I have two projects, one was UI and the other was API, and both have their own script in their respective package.json files.

So, here is what I did.

npm run --prefix react start&  npm run --prefix express start&

Simple node script to get you going without too much hassle. Using readline to combine outputs so the lines don't get mangled.

const { spawn } = require('child_process');
const readline = require('readline');

[
  spawn('npm', ['run', 'start-watch']),
  spawn('npm', ['run', 'wp-server'])
].forEach(child => {
    readline.createInterface({
        input: child.stdout
    }).on('line', console.log);

    readline.createInterface({
        input: child.stderr,
    }).on('line', console.log);
});

A simple and native way for Windows CMD

"start /b npm run bg-task1 && start /b npm run bg-task2 && npm run main-task"

(start /b means start in the background)

I had a similar need, and found using GNU parallel the simplest. My package.json looks like this:

"scripts": {
  "foo": "<invoke_foo>",
  "bar": "<invoke_bar>",
  "both": "parallel --ungroup 'npm run' ::: foo bar"
},

Then run both foo and bar with npm run both

Native solution in VScode using parallel tasks:

Ejecute it directly from the task manager F1 -> Task: Run Task -> Development and it will run both tasks in two separated shells in parallel using your scripts.

package.json

"scripts": {
    "start-watch": "nodemon run-babel index.js",
    "wp-server": "webpack-dev-server",
  }

.vscode\tasks.json

See the line with the following: "dependsOrder": "parallel"
Note: works in vscode in windows and linux

{
    "version": "2.0.0",
    "tasks": [
        {
          "label": "start-watch in package.json",
          "type": "npm",
          "script": "start-watch",
          "presentation": {
            "clear": true,
            "reveal": "silent",
            "showReuseMessage": true
          }
        },
        {
          "label": "wp-server in package.json",
          "type": "npm",
          "script": "wp-server",
          "presentation": {
            "clear": true,
            "reveal": "silent",
            "showReuseMessage": false
          }
        },
        {
          "label": "Development",
          "dependsOrder": "parallel",
          "dependsOn": ["start-watch in package.json", "wp-server in package.json"]
        },
        {
          "label": "Terminate All Tasks",
          "type": "shell",
          "command": "echo ${input:terminate}",
          "problemMatcher": []
        },
    ]
}

The only problem here is that unlike concurrently which runs the commands in the same shell where you run the concurrently command and you can kill both processes (ctrl+C) at the same time, with task they run in two different shells inside the VSCode terminal and can only be terminated separately or we could define another task that will terminate all the open tasks (see the task called Terminate All Task)

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