watsonerror-callsites
Yet another module for extracting callsites (a.k.a. stack-frames) from
Node.js Error objects.
Installation
npm install error-callsitesUsage
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:
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:
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 thiscallsite.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 functioncallsite.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 functioncallsite.getFileName()- if this function was defined in a script returns the name of the scriptcallsite.getLineNumber()- if this function was defined in a script returns the current line numbercallsite.getColumnNumber()- if this function was defined in a script returns the current column numbercallsite.getEvalOrigin()- if this function was created using a call to eval returns a CallSite object representing the location where eval was calledcallsite.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.