Pretty Exceptions

Pretty and more helpful uncaught exceptions, automatically.

Usage

Library

const pretty = require('pretty-exceptions/lib')

const options = {
  source: true,
  native: true,
  color: true,
  cwd: process.cwd()
}

const output = pretty(new Error('foo'), options)

options

CLI (preferred)

This is the preferred approach to best avoid mistakingly including into production builds

1. setup your NODE_PATH environment variable

   export NODE_PATH="$NODE_PATH:$(npm root -g)"
   

2. install pretty-exceptions

   npm install --global pretty-exceptions
   

3. run your application with the --require flag:

   node --require pretty-exceptions my-app.js
   
   # alternative modes (see below):
   node --require pretty-exceptions/source my-app.js
   

Pro Tip:

Use Bash Aliases for less typing

# make a special alias for debugging
alias node-ex='node --require pretty-exceptions'

# or even better:
alias node='node --require pretty-exceptions/source'

To make this persistent, you need to add this into your ~/.bashrc (or ~/.bash_profile).

Environment Variables

Source (if you really must!)

Require at the top-most entry point of your app:

require('pretty-exceptions')

// alternative modes (see below):
require('pretty-exceptions/source-native')

Modes

Default

$ node --require pretty-exceptions my-app.js

Output

Error: oh no! this is an error message!
 │
 └┬╼ /path/to/my-app.js
  │
  ├──╼ someOtherFunction @ line 2:27
  ├──╼ someFunction @ line 6:3
  └──╼ Object.<anonymous> @ line 9:1

Demo

Colors will vary based on your local terminal configuration

View Source

$ node --require pretty-exceptions/source my-app.js
# OR
$ PRETTY_EXCEPTIONS_SOURCE=1 node --require pretty-exceptions my-app.js

Output

Error: oh no! this is an error message!
 │
 └┬╼ /path/to/my-app.js
  │
  ├──╼ someOtherFunction @ line 2
  │
  │    function someOtherFunction () {
  ├╌╌╌╌╌╌╌╌╌╌╮
  │    throw new Error('oh no! this is an error message!')
  │    }
  │
  ├──╼ someFunction @ line 6
  │
  │    function someFunction () {
  ├╌╌╌╌╮
  │    someOtherFunction()
  │    }
  │
  ├──╼ Object.<anonymous> @ line 9
  │
  └╌╌╌╌╮
       someFunction()

Demo

Colors will vary based on your local terminal configuration

View Native Calls

$ node --require pretty-exceptions/native my-app.js
# OR
$ PRETTY_EXCEPTIONS_NATIVE=true node --require pretty-exceptions my-app.js

Output

Error: oh no! this is an error message!
 │
 ├─┬╼ /path/to/my-app.js
 │ │
 │ ├──╼ someOtherFunction @ line 2:27
 │ ├──╼ someFunction @ line 6:3
 │ └──╼ Object.<anonymous> @ line 9:1
 │
 ├─┬╼ module.js
 │ │
 │ ├──╼ Module._compile @ line 571:32
 │ ├──╼ Object.Module._extensions..js @ line 580:10
 │ ├──╼ Module.load @ line 488:32
 │ ├──╼ tryModuleLoad @ line 447:12
 │ ├──╼ Function.Module._load @ line 439:3
 │ └──╼ Module.runMain @ line 605:10
 │
 └┬╼ bootstrap_node.js
  │
  └──╼ run @ line 423:7

Demo

Colors will vary based on your local terminal configuration

View Source & Native

$ node --require pretty-exceptions/source-native my-app.js
# OR
$ PRETTY_EXCEPTIONS_SOURCE=1 PRETTY_EXCEPTIONS_NATIVE=1 node --require pretty-exceptions my-app.js

Output

Error: oh no! this is an error message!
 │
 ├─┬╼ /path/to/my-app.js
 │ │
 │ ├──╼ someOtherFunction @ line 2
 │ │
 │ │    function someOtherFunction () {
 │ ├╌╌╌╌╌╌╌╌╌╌╮
 │ │    throw new Error('oh no! this is an error message!')
 │ │    }
 │ │
 │ ├──╼ someFunction @ line 6
 │ │
 │ │    function someFunction () {
 │ ├╌╌╌╌╮
 │ │    someOtherFunction()
 │ │    }
 │ │
 │ ├──╼ Object.<anonymous> @ line 9
 │ │
 │ └╌╌╌╌╮
 │      someFunction()
 │ 
 │
 ├─┬╼ module.js
 │ │
 │ ├──╼ Module._compile @ line 571
 │ ├──╼ Object.Module._extensions..js @ line 580
 │ ├──╼ Module.load @ line 488
 │ ├──╼ tryModuleLoad @ line 447
 │ ├──╼ Function.Module._load @ line 439
 │ └──╼ Module.runMain @ line 605
 │
 └┬╼ bootstrap_node.js
  │
  └──╼ run @ line 423

Demo

Colors will vary based on your local terminal configuration

Author: Ahmad Nassri • Twitter: @AhmadNassri