Dissect Error

Parse some js error and extract a sort of usefull info like:

• type (SyntaxError, ReferenceError, etc)
• message
• error site
• line
• column
• code that threw the error
• file
• stack trace (parsed as array)

Works with runtime errors, syntax errors, node VM eval errors and plain eval errors

And have zero dependencies!

How to use?

1. Install it

npm install -S dissect-error

2. Import it

const dissect = require( 'dissect-error' );

3. Use it

try {
  // throw some error
} catch ( err ) {
  const info = dissect( err );
 
  console.log( info );
}

Properties

The dissect function return an object with the following properties:

property	description
.type	JS error types like: Error, SyntaxError, MyCustomError, etc
.message	The message from the error
.site	What threw the error, Eg. Object.eval
.line	Line # where the error happen
.column	Column # where the error happen
.stack	Array of frames from the stack trace, each frame is an object (see below)
.expression	Expression which threw the error. Eg: const 2 = 1;
.file	The file which threw the error. Eg: /app/project/index.js

The .stack returns an array of stack frames wich have the folowing properties

property	description
.site	What thre the error. Eg. Object.eval
.file	The file which threw the error
.line	Line # where the error happen
.column	Column # where the error happen

Use cases

Plain runtime errors

try {
  await IO();
} catch ( err ) {
  const parsed = dissect( err );
 
  // result
  parsed.line; // 2
  parsed.expression; // await IO();
  parsed.site; // IO;
}

Node VM errors

Node VM errors are a bit different as they are parsed relative to the code evaluated by the VM, instead of the context of the VM invokation.

const vm = require( 'vm' );
const dissect = require( 'dissect-error' );
 
const code = `
module.exports = ( => };
`;
 
const ctx = { module, require, console, global, process };
vm.createContext( ctx );
 
try {
  vm.runInNewContext( code, ctx, { displayErrors: true } );
} catch ( err ) {
  const parsed = dissect( err );
  
  // result 
  parsed.type; // SyntaxError
  parsed.message; // Unexpected token =>
  parsed.line; // 2 (relative to the "code" parsed by the node VM)
  parsed.expression; // 'module.exports = ( => };
}