99 lines
3.6 KiB
Markdown
99 lines
3.6 KiB
Markdown
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# stack-trace
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Get v8 stack traces as an array of CallSite objects.
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## Install
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``` bash
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npm install stack-trace
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```
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## Usage
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The stack-trace module makes it easy for you to capture the current stack:
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``` javascript
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var stackTrace = require('stack-trace');
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var trace = stackTrace.get();
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require('assert').strictEqual(trace[0].getFileName(), __filename);
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```
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However, sometimes you have already popped the stack you are interested in,
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and all you have left is an `Error` object. This module can help:
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``` javascript
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var stackTrace = require('stack-trace');
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var err = new Error('something went wrong');
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var trace = stackTrace.parse(err);
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require('assert').strictEqual(trace[0].getFileName(), __filename);
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```
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Please note that parsing the `Error#stack` property is not perfect, only
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certain properties can be retrieved with it as noted in the API docs below.
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## Long stack traces
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stack-trace works great with [long-stack-traces][], when parsing an `err.stack`
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that has crossed the event loop boundary, a `CallSite` object returning
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`'----------------------------------------'` for `getFileName()` is created.
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All other methods of the event loop boundary call site return `null`.
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[long-stack-traces]: https://github.com/tlrobinson/long-stack-traces
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## API
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### stackTrace.get([belowFn])
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Returns an array of `CallSite` objects, where element `0` is the current call
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site.
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When passing a function on the current stack as the `belowFn` parameter, the
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returned array will only include `CallSite` objects below this function.
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### stackTrace.parse(err)
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Parses the `err.stack` property of an `Error` object into an array compatible
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with those returned by `stackTrace.get()`. However, only the following methods
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are implemented on the returned `CallSite` objects.
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* getTypeName
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* getFunctionName
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* getMethodName
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* getFileName
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* getLineNumber
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* getColumnNumber
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* isNative
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Note: Except `getFunctionName()`, all of the above methods return exactly the
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same values as you would get from `stackTrace.get()`. `getFunctionName()`
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is sometimes a little different, but still useful.
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### CallSite
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The official v8 CallSite object API can be found [here][v8stackapi]. A quick
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excerpt:
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> A CallSite object defines the following methods:
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>
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> * **getThis**: returns the value of this
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> * **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.
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> * **getFunction**: returns the current function
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> * **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.
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> * **getMethodName**: returns the name of the property of this or one of its prototypes that holds the current function
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> * **getFileName**: if this function was defined in a script returns the name of the script
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> * **getLineNumber**: if this function was defined in a script returns the current line number
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> * **getColumnNumber**: if this function was defined in a script returns the current column number
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> * **getEvalOrigin**: if this function was created using a call to eval returns a CallSite object representing the location where eval was called
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> * **isToplevel**: is this a toplevel invocation, that is, is this the global object?
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> * **isEval**: does this call take place in code defined by a call to eval?
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> * **isNative**: is this call in native V8 code?
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> * **isConstructor**: is this a constructor call?
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[v8stackapi]: http://code.google.com/p/v8/wiki/JavaScriptStackTraceApi
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## License
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stack-trace is licensed under the MIT license.
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