Develop Reference

How to fix npm start errors on my nodejs?

After the npm install, I tried npm start for my project. But it shows an error. How can we fix this error?enter image description here

You're in the wrong directory.
cd 02-exrpess-tutorial
npm install (in case you're missing any dependencies)
npm start

There's no package.json at the directory where you are trying to run the command. Likely you want to run npm start in one of the subdirectories.

first go the correct file directory.
usually cd "app-name"
(It display this after you create a new app).

you're in the wrong file directory ;

'vue' is not recognized as an internal or external command

everything was installed correctly. but whenever I try to create project, it says "'vue' is not recognized as an internal or external command". I installed and re-installed but didn't work. npm was also added to environmental variable path.
C:\Users\touha\Desktop>npm list -g --depth=0
C:\Users\touha\.npm-packages
`-- #vue/cli#3.8.2
C:\Users\touha\Desktop>vue ui
'vue' is not recognized as an internal or external command,
operable program or batch file.
C:\Users\touha\Desktop>

Locate vue.cmd and add its location to your PATH
It is added to package manager(npm or yarn) installation. So you may find it at following locations
YARN
C:\Users{YourAccount}\AppData\Local\Yarn\bin
NPM
C:\Users{YourAccount}\AppData\Roaming\npm

just open PowerShell and run: npm install -g #vue/cli

Addition: If setting the path variable and reinstalling #vue/cli does not work, using the node.js command prompt instead might solve the issue.

It seems vue isn't been installed globally for some reasons.
This is the step I followed to solve mine:
Firstly, create your desired project folder (say "Vue Project"). This is where you want to create a vue project.
Then create a "node_modules" folder in the Vue Project folder
Then go to your system npm folder C:\Users{YourAccount}\AppData\Roaming\npm
You will see three different "vue" files. Copy them and paste in the Vue Project Folder you created.
Go back to C:\Users{YourAccount}\AppData\Roaming\npm and enter the node_modules folder. You'll see a "#vue" folder. Copy this, and paste it in the node_modules folder you created in the Vue Project Folder.
You can now head back to the CLI and create your project using "vue create my-vue-project" where my-vue-project is your desired vue project name.

You can try this way it worked for me
go to the location of your yarn or npm mine is C:\Users\TED\AppData\Local\Yarn\bin for Yarn
C:\Users\TED\AppData\Local\Npm\bin for Npm users
TED will be replaced by your user name
then copy and add it to your system environment variable
Note in case you don't find AppData make sure you have view hidden file checked

I am using Yarn to install #vue/cli.
The way I solve it is via the following steps
Locate your global installed vue.cmd location
Add the vue.cmd directory into System variable Env. For myself, the path is C:\Users{MyAccount}\AppData\Local\Yarn\.bin

what worked for me:
In a powershell :
npm install vue
npm install -g #vue/cli
C:\Users\{USER}\AppData\Roaming\npm\vue.cmd create {NAME}

if you got this error most probably chance package not installed completely
check-in C:\Users\dev\AppData\Roaming\npm
if you had not found the package under this folder then re-run your command

Run command prompt as administrator
Run setx /M path "%path%;%appdata%\npm
Restart the command prompt
Now create the Vue project

how do i run jest test on a node_modules folder in react

I have added my own another project as a dependency. now it's on the node_modules folder now
how do I run test file on that folder when running the npm test

I don't know what your needs are but this is wrong.
If you want your project to be a dependency there are other safest ways to do that.
For example, with yarn, you can install a package from your computer as a dependency.
Consider the following example: you have your main-project, in which you want to include your sub-project.
So, in your main-project directory you can run yarn add ../path/to/sub-project and yarn will copy the code of your sub-project into the main-project. In this way you can keep the code splitted in two different reporitories.
A better way, if your sub-project is on github, bitbucket or whatever, is to give to yarn the url of your repo.
Yarn will automatically clone the repo into your node_modules every time that you'll run yarn. You can also specify a specific commit to use.
Read more about that in the yarn documentation.

npm list is never empty

I have created a folder for a new project and I'm about to install a package via npm, but before that I run npm list and it has a lot stuff there.
Shouldn't it be empty? What am I doing wrong?

Check if you have node_modules somewhere in the parent directories. When npm is looking for node_modules in current directory with no success, it will look in parent directory and so on.

Node.js project with no package.json

Is it ok to have a node.js project with no package.json? The ones I see on the internet all come with package.json
What is the effect of having no package.json?
How is package.json created in the first place? Is it created automatically? I am wondering why I do not have package.json

Fundamentally, package.json is a meta file for your application. It lists all the configuration of your application.
What is the effect of having no package.json?
Nothing as far as you're running all your code locally and have no requirement for deployment whatsoever.
Let's setup a scene for you to understand this better.
Imagine that you wrote a brilliant application using node. Now all the chicks in your surrounding want it to play with. It is so fantastic!
Now you want to give it to them and during the development process you `npm install`ed so many things that your project grows beyond 4TB size.
There is no data storage device available to ship that huge code base.
Then the girl of your dream said I want it and I want it now. So you begin searching for app deployment process for node applications.
That is where you stumble upon a magical thing called package.json.
So what you do is you list all your npm installed modules under dependencies property. Then you delete node_modulesfolder, add package.json and commit the entire damn thing in github. Even the .zip file is of 10MB
Then she gets the code.
Types in npm install && npm start (which will install all the dependencies from the package.json` and start your application)
If you have package.json however, that is where you specify all your dependencies.
Using --save flag of npm install
Example.
npm install express --save
How is package.json created in the first place? Is it created automatically?
You can manually create a text file and save it as package.json
OR
A more sophisticated way is to use the command
npm init
I am wondering why I do not have package.json
Me too! :)
You're most probably following a tutorial that doesn't emphasize on initial configuration of the project OR the author of those tutorials presume that the reader has all the fundamentals down to begin with.

It is created automatically if you write npm init.
Then, every package you add using npm install packagename --save will be added to the dependencies list.
You need package.json so that when you want to use your project on another machine you don't have to copy all node_modules, but only your .js files you have written, assets and package.json. You can then run npm install command and it will automatically download and install all the required modules (found in the list of dependencies inside package.json).
You can also manually create or edit it, but it's easier to add --save when installing a module so you don't have to worry about package versions and stuff like that.
Also if you want to create a npm package, an open source project or stuff other people will use, it's either required or the norm to have this package.json file describing your project.

package.json is npm file, if you don't use npm you will not have this file, npm is a great tool if you want to use external libraries in your project but if you don't need it (which is very not likely unless you are doing something very simple), you don't need package.json file too.
To generate package.json file initialize npm in your project using npm init

possible reason thus it exist is you maybe you enter a wrong command like npm i -y, you must initialize the project first, just enter a command npm init -y
Welcome.

Well, if you are running it on your local machine, it's fine. now to answer your last question, package.json is not created automatically.
the npm command npm init -y creates the 'package.json' file. It basically makes sharing your code and installing your codebase easier.