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78 lines
1.6 KiB
Markdown
78 lines
1.6 KiB
Markdown
makeerror [](http://travis-ci.org/nshah/nodejs-makeerror)
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=========
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A library to make errors.
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Basics
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------
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Makes an Error constructor function with the signature below. All arguments are
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optional, and if the first argument is not a `String`, it will be assumed to be
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`data`:
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```javascript
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function(message, data)
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```
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You'll typically do something like:
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```javascript
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var makeError = require('makeerror')
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var UnknownFileTypeError = makeError(
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'UnknownFileTypeError',
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'The specified type is not known.'
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)
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var er = UnknownFileTypeError()
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```
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`er` will have a prototype chain that ensures:
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```javascript
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er instanceof UnknownFileTypeError
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er instanceof Error
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```
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Templatized Error Messages
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--------------------------
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There is support for simple string substitutions like:
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```javascript
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var makeError = require('makeerror')
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var UnknownFileTypeError = makeError(
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'UnknownFileTypeError',
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'The specified type "{type}" is not known.'
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)
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var er = UnknownFileTypeError({ type: 'bmp' })
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```
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Now `er.message` or `er.toString()` will return `'The specified type "bmp" is
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not known.'`.
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Prototype Hierarchies
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---------------------
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You can create simple hierarchies as well using the `prototype` chain:
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```javascript
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var makeError = require('makeerror')
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var ParentError = makeError('ParentError')
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var ChildError = makeError(
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'ChildError',
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'The child error.',
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{ proto: ParentError() }
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)
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var er = ChildError()
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```
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`er` will have a prototype chain that ensures:
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```javascript
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er instanceof ChildError
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er instanceof ParentError
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er instanceof Error
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```
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