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fault

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Functional errors with formatted output.

Contents

What is this?

This package adds printf-like interpolation to errors.

When should I use this?

This package useful when you frequently display parameters in error messages and manual string concatenation is becoming verbose.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install fault

In Deno with esm.sh:

import {fault} from 'https://esm.sh/fault@2'

In browsers with esm.sh:

<script type="module">
  import {fault} from 'https://esm.sh/fault@2?bundle'
</script>

Use

import {fault} from 'fault'

throw fault('Hello %s!', 'Eric')

Yields:

Error: Hello Eric!
    at FormattedError (~/node_modules/fault/index.js:30:12)
    at Object.<anonymous> (~/example.js:3:7)
    …

Or, format a float in a type error:

import {fault} from 'fault'

throw fault.type('Who doesn’t like %f? 🍰', Math.PI)

Yields:

TypeError: Who doesn’t like 3.141593? 🍰
    at Function.FormattedError [as type] (~/node_modules/fault/index.js:30:12)
    at Object.<anonymous> (~/example.js:3:7)

API

This package exports the following identifiers: fault and create. There is no default export.

fault(format?[, values…])

Create an error with a printf-like formatted message.

Parameters
  • format (string, optional) — template string
  • values (*, optional) — values to render in format
Returns

An Error instance.

Formatters

The following formatters are supported in format:

  • %s — string
  • %b — binary
  • %c — character
  • %d — decimal
  • %f — floating point
  • %o — octal
  • %x — lowercase hexadecimal
  • %X — uppercase hexadecimal
  • % followed by any other character, prints that character

See samsonjs/format for argument parsing.

Other errors

create(Constructor)

Factory to create instances of ErrorConstructor with support for formatting. Used internally to wrap the global error constructors and exposed for custom errors. Returns a function just like fault.

Types

This package is fully typed with TypeScript. There are no extra exported types.

Compatibility

This package is at least compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, and 16.0+. It also works in Deno and modern browsers.

Security

This package is safe.

Related

Contribute

Yes please! See How to Contribute to Open Source.

License

MIT © Titus Wormer