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https://github.com/GoogleChromeLabs/ndb

ndb is an improved debugging experience for Node.js, enabled by Chrome DevTools
https://github.com/GoogleChromeLabs/ndb

debugging devtools nodejs

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ndb is an improved debugging experience for Node.js, enabled by Chrome DevTools

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README 

        
# ndb



[![Build Status](https://img.shields.io/travis/com/GoogleChromeLabs/ndb/master.svg)](https://travis-ci.com/GoogleChromeLabs/ndb)

[![NPM ndb package](https://img.shields.io/npm/v/ndb.svg)](https://npmjs.org/package/ndb)






> ndb is an improved debugging experience for Node.js, enabled by Chrome DevTools



## Installation



Compatibility: ndb requires Node >=8.0.0. It works best with Node >=10.



Installation: ndb depends on [Puppeteer](https://github.com/GoogleChrome/puppeteer) which downloads a recent version of Chromium (~170MB Mac, ~280MB Linux, ~280MB Win).



```bash

# global install with npm:

npm install -g ndb



# alternatively, with yarn:

yarn global add ndb

```



Global installation may fail with different permission errors, you can find help in this [thread](https://github.com/GoogleChromeLabs/ndb/issues/20).



Windows users: Installation may fail on Windows during compilation the native dependencies. The following command may help: `npm install -g windows-build-tools`



### Local install



If you want ndb available from an npm script (eg. `npm run debug` runs `ndb index.js`), you can install it as a development dependency:



```bash

# local install with npm:

npm install --save-dev ndb



# alternatively, with yarn:

yarn add ndb --dev

```



You can then [set up an npm script](https://docs.npmjs.com/misc/scripts#examples). In this case, ndb will not be available in your system path.



## Getting Started



You can start debugging your Node.js application using one of the following ways:



- Use `ndb` instead of the `node` command



```bash

ndb server.js



# Alternatively, you can prepend `ndb`

ndb node server.js

```



- Prepend `ndb` in front of any other binary



```bash

# If you use some other binary, just prepend `ndb`

## npm run unit

ndb npm run unit



# Debug any globally installed package

## mocha

ndb mocha



# To use a local binary, use `npx` and prepend before it

ndb npx mocha

```



- Launch `ndb` as a standalone application 

   - Then, debug any npm script from your `package.json`, e.g. unit tests



```bash

# cd to your project folder (with a package.json)

ndb .

# In Sources panel > "NPM Scripts" sidebar, click the selected "Run" button 

```



- Use `Ctrl`/`Cmd` + `R` to restart last run

- Run any node command from within ndb's integrated terminal and ndb will connect automatically

- Run any open script source by using 'Run this script' context menu item, ndb will connect automatically as well



- Use `--prof` flag to profile your app, `Ctrl`/`Cmd` + `R` restarts profiling

```bash

ndb --prof npm run unit

```



## What can I do?



`ndb` has some powerful features exclusively for Node.js:

1. Child processes are detected and attached to.

1. You can place breakpoints before the modules are required.

1. You can edit your files within the UI. On Ctrl-S/Cmd-S, DevTools will [save the changes to disk](https://developers.google.com/web/tools/chrome-devtools/workspaces/).

1. By default, ndb [blackboxes](https://developers.google.com/web/tools/chrome-devtools/javascript/reference#blackbox) all scripts outside current working directory to improve focus. This includes node internal libraries (like `_stream_wrap.js`, `async_hooks.js`, `fs.js`) This behaviour may be changed by "Blackbox anything outside working dir" setting. 



In addition, you can use all the DevTools functionality that you've used in [typical Node debugging](https://medium.com/@paul_irish/debugging-node-js-nightlies-with-chrome-devtools-7c4a1b95ae27):

- breakpoint debugging, async stacks (AKA long stack traces), [async stepping](https://developers.google.com/web/updates/2018/01/devtools#async), etc...

- console (top-level await, object inspection, advanced filtering)

- [eager evaluation](https://developers.google.com/web/updates/2018/05/devtools#eagerevaluation) in console (requires Node >= 10)

- JS sampling profiler

- memory profiler



### Screenshot

![image](https://user-images.githubusercontent.com/39191/43023843-14a085a6-8c21-11e8-85b7-b9fd3405938a.png)



## Contributing



Check out [contributing guide](https://github.com/GoogleChromeLabs/ndb/blob/master/CONTRIBUTING.md) to get an overview of ndb development.



#### Thanks to the 'OG' `ndb`



In early 2011, [@smtlaissezfaire](https://github.com/smtlaissezfaire) released the first serious debugger for Node.js, under the `ndb` package name. It's still preserved at [github.com/smtlaissezfaire/ndb](https://github.com/smtlaissezfaire/ndb#readme). We thank Scott for generously donating the package name.