I am new to NodeJS and I just discovered node inspector.
The command I usually run in order to start my application is npm start (I use the Express framework) but when I want to debug, I need to run node-debug followed by a specific file.
In the official documentation of node inspector it says that in order to start the debugger I need to type :
$ node-debug app.js
But when I do it simply debugs the app.js file instead of running the server and starting the application.
What is the command I should run in order to debug the whole express application instead of only the app.js file?
When we type npm start the express framework looks at package.json file and executes the file next to the start : tag.
For express, this directory is ./bin/www so the correct command is node-debug bin/www ran from the parent directory instead of node-debug app.js.
Related
I stareted my node app with node index.js and got the following message:
(node:10128) UnhandledPromiseRejectionWarning: TypeError: e.reduce is not a function
at Module.te (C:\Projects\myproject\node_modules\tronweb\dist\TronWeb.node.js:1:9236)
Now I'm interessted in whats happening. I've seen that there are mapping files TronWeb.node.js.map in the tronweb\dist directory. I started again using --inspect and opened the chrome dev tools. But in the console I see exactly the same message.
In Node v12.12.0+ sourcemaps are supported natively. Pass --enable-source-maps flag to enable them.
One caveat in Node v12.12.0 is that Error.prepareStackTrace will no longer be called when source maps are enabled. This was fixed in v12.16+.
You can use https://www.npmjs.com/package/source-map-support
$ npm install source-map-support --save-dev
Then change your run command in package.json to:
node -r source-map-support/register index.js
(Note that you should have an index.map.js next to index.js)
I have an Electron application that run into a node.js server. And I also want to work with "nodemon" for live execution node server.
This 2 previous sentences getting up 3 different execution possible into start key in package.json file :
electron .
node server.js
nodemon server.js
I would like quickly switch between those execution command. I can create a Run/Config template with PhpStorm but all of those save command run with the same package.json file that wrote the start command.
How can I use the same package.json for working with 3 execution environments?
Would it be possible to get an explanation of how npm start works?
I have an Angular 2 application written in Typescript. I enter npm start in the console and this both compiles and launches the application using Node's built in web server.
However what is the starting point for this? Which files does the npm start command read in order to compile and start the application? Also why do I use npm start and not e.g. node start? I understood that NPM was just the package manager for node itself.
What I understand so far:
I have a tsconfig.js file which tells the TypeScript compiler what to do.
I have a packages.json file which tells node which packages to download.
Where do the following files fit into this:
main.ts
app/app.module.ts - which I understand is the starting point for my application.
How do all of these components fit together to form the application?
npm start is just an alias for npm run start, which runs whatever command is in scripts.start in your package.json.
It neither knows nor cares about TypeScript, or Angular, or anything like that - it just executes whatever script it's given on the command line.
I am new to node. I am trying to run an express server. I get no errors when installing express but when i run npm start or node app (as all the beginner tutorials point) nothing seems to be happening. The only way i can start the server is by typing node /bin/www. My operating system is Windows. Any advice?
The Express scaffold script generates a package.json file with a start script field that points to the app.js file it also created. Since Express 4 was released the scaffold generator script has been moved to its own package. https://github.com/expressjs/generator
All npm start does is look in the package.json file for a starting script to pass to node. You can see this in the documentation.
Running npm start with a package.json like this:
"scripts": {
"start": "app.js"
}
Is exactly equivalent to running node app.js.
I managed to solve my issue by changing the code page of cmd-dos. By using chcp 850 or chcp 65001 in cmd thus changing codepage to latin - utf8 the issue is gone.
In order to debug with node-inspector I need to start my app with the node --debug command. Up to this point I have only used sails lift to start my Sails.js app, so I am unsure of how to start my app using the normal node command.
So you can actually launch a sails project with node app.js --debug if you have sails installed in your project, rather than only system-wide. Go to your project's root directory and run npm install. Sails should already be in your package.json and thus should install to your project directory.
As of Sails v0.10.x, you can do sails debug instead of sails lift.
sails inspect since Sails v1.0
As of sails v1.0, sails debug is deprecated for newer Node.js, and you should instead use sails inspect.
This is documented at: https://sailsjs.com/documentation/reference/command-line-interface/sails-inspect and is presumably done to match the newer node --inspect interface.
Have you tried using node-webkit to run your node.js apps? This is what we use at work to debug our node.js server applications. It is quite useful runtime based on chromium which you can use to inspect your code using familiar breakpoints, stack traces, variable inspection and such without having to rely on node-inspector (which I find hard to use to be honest).
What you do is instead of using console command 'node you-app.js' you set the node-webkit to launch your app, run the webkit then open its console (which is the same as console in Chrome browser) and from there you can open your source files and start debugging like any other client side JavaScript code.
node inspect
You can also use the command line debugger with:
node inspect app.js
This stops at the beginning, so do a continue:
c
And now, when your code with a statement:
debugger
gets executed, you fall into the Node CLI debugger as usual.
Tested on Sail v1.1, Node v10.15.1, Ubuntu 18.10.
nodemon --inspect and nodemon inspect
You can use those to inspect when using nodemon, which automatically reloads the app on file save: Auto reloading a Sails.js app on code changes?
Those options are analogous to node inspect and node --inspect: node inspect works with debugger statements, and node --inspect works with the Chrome debugger.
Especially useful with the "Open dedicated DevTools for Node" feature: Can I get node --inspect to open Chrome automatically
nodemon inspect is a bit annoying as it requires a continue everytime you make any app changes and nodemon restarts the server. TODO find a way around it.