> For the complete documentation index, see [llms.txt](https://bryan-guner.gitbook.io/my-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bryan-guner.gitbook.io/my-docs/redux/repos/examples/real-world/node_modules/makeerror.md).

# makeerror

A library to make errors.

## Basics

Makes an Error constructor function with the signature below. All arguments are optional, and if the first argument is not a `String`, it will be assumed to be `data`:

```javascript
function(message, data)
```

You'll typically do something like:

```javascript
var makeError = require('makeerror')
var UnknownFileTypeError = makeError(
  'UnknownFileTypeError',
  'The specified type is not known.'
)
var er = UnknownFileTypeError()
```

`er` will have a prototype chain that ensures:

```javascript
er instanceof UnknownFileTypeError
er instanceof Error
```

## Templatized Error Messages

There is support for simple string substitutions like:

```javascript
var makeError = require('makeerror')
var UnknownFileTypeError = makeError(
  'UnknownFileTypeError',
  'The specified type "{type}" is not known.'
)
var er = UnknownFileTypeError({ type: 'bmp' })
```

Now `er.message` or `er.toString()` will return `'The specified type "bmp" is not known.'`.

## Prototype Hierarchies

You can create simple hierarchies as well using the `prototype` chain:

```javascript
var makeError = require('makeerror')
var ParentError = makeError('ParentError')
var ChildError = makeError(
  'ChildError',
  'The child error.',
  { proto: ParentError() }
)
var er = ChildError()
```

`er` will have a prototype chain that ensures:

```javascript
er instanceof ChildError
er instanceof ParentError
er instanceof Error
```


---

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