Buckets:
| # node-error-ex [](https://travis-ci.org/Qix-/node-error-ex) [](https://coveralls.io/r/Qix-/node-error-ex) | |
| > Easily subclass and customize new Error types | |
| ## Examples | |
| To include in your project: | |
| ```javascript | |
| var errorEx = require('error-ex'); | |
| ``` | |
| To create an error message type with a specific name (note, that `ErrorFn.name` | |
| will not reflect this): | |
| ```javascript | |
| var JSONError = errorEx('JSONError'); | |
| var err = new JSONError('error'); | |
| err.name; //-> JSONError | |
| throw err; //-> JSONError: error | |
| ``` | |
| To add a stack line: | |
| ```javascript | |
| var JSONError = errorEx('JSONError', {fileName: errorEx.line('in %s')}); | |
| var err = new JSONError('error') | |
| err.fileName = '/a/b/c/foo.json'; | |
| throw err; //-> (line 2)-> in /a/b/c/foo.json | |
| ``` | |
| To append to the error message: | |
| ```javascript | |
| var JSONError = errorEx('JSONError', {fileName: errorEx.append('in %s')}); | |
| var err = new JSONError('error'); | |
| err.fileName = '/a/b/c/foo.json'; | |
| throw err; //-> JSONError: error in /a/b/c/foo.json | |
| ``` | |
| ## API | |
| #### `errorEx([name], [properties])` | |
| Creates a new ErrorEx error type | |
| - `name`: the name of the new type (appears in the error message upon throw; | |
| defaults to `Error.name`) | |
| - `properties`: if supplied, used as a key/value dictionary of properties to | |
| use when building up the stack message. Keys are property names that are | |
| looked up on the error message, and then passed to function values. | |
| - `line`: if specified and is a function, return value is added as a stack | |
| entry (error-ex will indent for you). Passed the property value given | |
| the key. | |
| - `stack`: if specified and is a function, passed the value of the property | |
| using the key, and the raw stack lines as a second argument. Takes no | |
| return value (but the stack can be modified directly). | |
| - `message`: if specified and is a function, return value is used as new | |
| `.message` value upon get. Passed the property value of the property named | |
| by key, and the existing message is passed as the second argument as an | |
| array of lines (suitable for multi-line messages). | |
| Returns a constructor (Function) that can be used just like the regular Error | |
| constructor. | |
| ```javascript | |
| var errorEx = require('error-ex'); | |
| var BasicError = errorEx(); | |
| var NamedError = errorEx('NamedError'); | |
| // -- | |
| var AdvancedError = errorEx('AdvancedError', { | |
| foo: { | |
| line: function (value, stack) { | |
| if (value) { | |
| return 'bar ' + value; | |
| } | |
| return null; | |
| } | |
| } | |
| } | |
| var err = new AdvancedError('hello, world'); | |
| err.foo = 'baz'; | |
| throw err; | |
| /* | |
| AdvancedError: hello, world | |
| bar baz | |
| at tryReadme() (readme.js:20:1) | |
| */ | |
| ``` | |
| #### `errorEx.line(str)` | |
| Creates a stack line using a delimiter | |
| > This is a helper function. It is to be used in lieu of writing a value object | |
| > for `properties` values. | |
| - `str`: The string to create | |
| - Use the delimiter `%s` to specify where in the string the value should go | |
| ```javascript | |
| var errorEx = require('error-ex'); | |
| var FileError = errorEx('FileError', {fileName: errorEx.line('in %s')}); | |
| var err = new FileError('problem reading file'); | |
| err.fileName = '/a/b/c/d/foo.js'; | |
| throw err; | |
| /* | |
| FileError: problem reading file | |
| in /a/b/c/d/foo.js | |
| at tryReadme() (readme.js:7:1) | |
| */ | |
| ``` | |
| #### `errorEx.append(str)` | |
| Appends to the `error.message` string | |
| > This is a helper function. It is to be used in lieu of writing a value object | |
| > for `properties` values. | |
| - `str`: The string to append | |
| - Use the delimiter `%s` to specify where in the string the value should go | |
| ```javascript | |
| var errorEx = require('error-ex'); | |
| var SyntaxError = errorEx('SyntaxError', {fileName: errorEx.append('in %s')}); | |
| var err = new SyntaxError('improper indentation'); | |
| err.fileName = '/a/b/c/d/foo.js'; | |
| throw err; | |
| /* | |
| SyntaxError: improper indentation in /a/b/c/d/foo.js | |
| at tryReadme() (readme.js:7:1) | |
| */ | |
| ``` | |
| ## License | |
| Licensed under the [MIT License](http://opensource.org/licenses/MIT). | |
| You can find a copy of it in [LICENSE](LICENSE). | |
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