error-callsites

Yet another module for extracting callsites (a.k.a. stack-frames) from
Node.js Error objects.


Installation

``
npm install error-callsites
`

Usage

`js
var callsites = require('error-callsites')

var err = new Error('foo')
var frames = callsites(err)

console.log('Error occurred on line', frames[0].getLineNumber())
`

API

The module exposes a single function which expects an Error object as
the first argument:

`js
var frames = callsites(err)
`

More specifically, it expects an object on which Error.captureStackTrace(obj)
has been called, which is the case for Error objects. You can do it directly
yourself:

`js
var obj = {}
Error.captureStackTrace(obj)
var frames = callsites(err)
`

The function returns an array of
v8 CallSite objects
-- one for each frame in the stack trace. CallSite objects provide accessor
methods for information on that frame. For example:

- callsite.getThis() - returns the value of this
- callsite.getTypeName() - returns the type of this as a string. This is the name of the function stored in the constructor field of this, if available, otherwise the object's [[Class]] internal property.
- callsite.getFunction() - returns the current function
- callsite.getFunctionName() - returns the name of the current function, typically its name property. If a name property is not available an attempt will be made to try to infer a name from the function's context.
- callsite.getMethodName() - returns the name of the property of this or one of its prototypes that holds the current function
- callsite.getFileName() - if this function was defined in a script returns the name of the script
- callsite.getLineNumber() - if this function was defined in a script returns the current line number
- callsite.getColumnNumber() - if this function was defined in a script returns the current column number
- callsite.getEvalOrigin() - if this function was created using a call to eval returns a CallSite object representing the location where eval was called
- callsite.isToplevel() - is this a toplevel invocation, that is, is this the global object?
- callsite.isEval() - does this call take place in code defined by a call to eval?
- callsite.isNative() - is this call in native V8 code?
- callsite.isConstructor() - is this a constructor call?

See the link above for a complete list of the accessor methods. Some have been
added in more recent versions of v8 and Node.js.

How it works

This package works by setting a custom Error.prepareStackTrace
property that transparently captures the structured stack trace that v8 passes
to this API, while also supporting other Node.js code in the process setting
its own Error.prepareStackTrace`.

License

MIT