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- # node-error-ex [![Travis-CI.org Build Status](https://img.shields.io/travis/Qix-/node-error-ex.svg?style=flat-square)](https://travis-ci.org/Qix-/node-error-ex) [![Coveralls.io Coverage Rating](https://img.shields.io/coveralls/Qix-/node-error-ex.svg?style=flat-square)](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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