I have a server.js file that I downloaded from someone's website. The first line is: var express=require('express');
When I try to run this server with "node server.js" I get the following error: "Cannot find module 'express'." The express module is installed in the default node install location:
C:\Users\myname\node_modules\express\
I'm able to successfully run express by executing "node express.js" from the express install location in node_modules. I also tried copying over the express folder and file into my c:\node-testing\ directory where my server.js file is located but I still get the error. Any idea what the problem might be and how to fix?
You can set the NODE_PATH environment variable to tell nodejs to search other paths for globally installed modules that are not in the project directory.
See http://nodejs.org/api/modules.html#modules_loading_from_the_global_folders for details.
On Unix installations there are some built-in default locations, but on Windows, it appears you have to set this environment variable manually to support a global location.
FYI, if you want require to load a module from the project directory, then you have to use
require("./filename");
with the ./ in front of it. That's why it didn't work when you copied it to the project directory. node makes a distinction between loading from the project directory vs. loading from the node_modules directory below and thus requires a different syntax to specify which one you want. Express.js is also not a stand-alone module because it depends on a bunch of other modules so you could not copy only it. I'd recommend using the NODE_PATH option or install express into your project directory (it will end up in a node_modules sub-directory).
Node.js will only search for modules in from the current (and parent) directories. Unlike npm, Node has no concept of "global" modules.
You need to run npm install to install your modules into the directory containing your code.
Related
I have the following dir structure:
src/
app/
package.json
node_modules/
app.js
tools/
tool_A.js
tool_A.js requires the express package
app.js requires tool_A
I have defined the express package in the requirements for app/package.json and it was correctly installed in the node_modules folder.
The issue is that if I run app/app.js I still get the error:
Error: Cannot find module 'express'
Is there a way to make it search the modules starting from the root app, rather than the outside directory?
You can move the package.json to the root directory and use require("../tools/toolA.js") inside of app.js.
Alternatively you create a new package inside of tools and install express for that package:
.../src/tools> npm init
[...]
.../src/tools> npm i express
Given your description, it seems as though the first solution is more appropriate for your situation, but both theoretically work.
EDIT:
Theoretically, though it's anything but clean, you could also use require("../app/node_modules/express"), but that would break as soon as the path to the express module changes.
I installed node package via npm install and the Data is located in the node_modules directory as own directory.
But if re-lift and afterwards access a function of this new module, the browser told me, function not defined.
Do I need to add the path of the .js file in the layout or anywhere else?
I know I can install Node.js libraries with the command npm from the command line... So, if I type:
npm install mylibrary
It'll create a node_modules folder on my current location and it'll install mylibrary (if it exists on npm)... Let's say that I create a Node.js code using it as the following:
const mylibrary = require('mylibrary')
mylibrary.doSomething()
Since I've installed this library on my current folder with the last command, this node.js script will work only if I save it on a file on my terminal current location as well. If I name this file as file.js, I can execute it with:
node file.js
Well, my problem is that I have a very specific case where the node_modules folder cannot exist in the same location that my file.js. Also, I'd like to avoid having to install mylibrary globally. Is there any way of defining as a parameter the path that the command node will search for the node_modules folder? I've checked node --help and it seems there's a lot of options, but I didn't manage to make it work. Is it possible to do? Can I use a node_modules folder that's neither the one of my file.js path or a global installed library?
You can have a link for the node_modules folder. For example, to create the symbolink link in Linux do this:
cd /path/to/script/folder
ln -s /path/to/where/you/can/have/node_modules node_modules
If you can't have the link, use the full path to the node_modules folder in the require, for example:
const mylibrary = require('/path/to/node_modules/mylibrary')
Also, you can solve the problem by using the NODE_PATH environment variable, set it like this
export NODE_PATH=/path/to/node_modules
I am quite new to programming and today decided to attempt and create a node.js and puppeteer project with the purpose of scraping website into a .txt file. I ran into issues straight away since for the most part I have no idea what I'm doing. After installing node.js and puppeteer, I was guided by some videos and articles I found to create my first project. In the command prompt using mkdir and later cd I was able to create and access the new directory, but I started running into problems with npm init. It only places the file package.json in the repository, but there isn't a package-lock or node_modules file anywhere. No idea what they do but thought this was a problem. When I open cmd and try to run the app by typing node app.js it returns Error: Cannot find module 'C:\Users\emili\app.js' along with some other gobble. What should I do, to be able to run the simple application I wrote?
It seems that you are missing some key knowledge on how NodeJS works, but in order to fix your issue (for now), you will need to take a few steps.
First, in your working directory (where the package.json is), you'll need to install your modules.
Run npm install puppeteer. This will do two things, create the node_modules folder and create the package-lock.json file.
Create a file named app.js (either manually or by running the command touch app.js) in your working directory, and put the following content inside of it:
console.log('Hello, World!');
Save the changes to app.js and then run node app.js in your terminal. You should see Hello, World! output to the terminal.
The reason npm install puppeteer created the node_modules folder and the package-lock.json file is because they weren't needed beforehand.
When you run npm install PACKAGE_NAME, you're installing a module (otherwise known as a package), thus it creates the node_modules folder so that it will have a place to put the module so that your code can access it. It also creates the package-lock.json file, which is used to track the module versions inside of your project.
With this information, I request you go back to the tutorial you were originally following and try going through it again and attempting to understand each of the core concepts before writing any real code.
I put some common code in this local module called 'client-common'. In one of the app project using this common module, I add this to package.json dependencies:
"client-common": "../client-common"
After npm install the module gets copied to node_modules. When I run (it's an Ionic project) ionic serve, it builds all fine, but at runtime in the browser I get
Runtime Error
Cannot find module "client-common"
I'm assuming this is a webpack issue? The question is why is the local module treated differently and not bundled at all?
It seems that I was supposed to supply an index.js in the common module. After adding an index.js duplicated from the existing index.d.ts, exporting everything, it just works now.