ono (Oh No!)

Throw better errors.

Features

• Formatted error messages, using Node's util.format() or your own custom formatter
• Wrap and re-throw an error without losing the original error's message and stack trace
• Add custom properties to your errors — great for error codes, support numbers, help URLs, etc.
• Errors can be serialized as JSON, including all native and custom properties
• Tested in Node, IO.js, and all modern web browsers on Mac, Windows, Linux, iOS, and Android

Example

// Throw an error with formatted message
throw ono("%s is invalid. Must be at least %d characters.", username, minLength);

// Wrap and re-throw an error without losing the original error's message and stack
throw ono(err, "An error occurred while saving your changes");

// Throw an error with custom properties (even a custom method!)
throw ono({code: 413, status: "Invalid data", retry: function() {...}});

// Add custom properties to an existing Error
throw ono(err, {code: 413, status: "Invalid data", retry: function() {...}})

// Any of the above can throw a specific Error subtype instead
throw ono.range(...);       // RangeError
throw ono.syntax(...);      // SyntaxError
throw ono.reference(...);   // ReferenceError

Installation

Node

Install using npm:

npm install ono

Then require it in your code:

var ono = require("ono");

Web Browsers

Install using bower:

bower install ono

Then reference ono.js or ono.min.js in your HTML:

<script src="bower_components/ono/dist/ono.js"></script>

Or, if you're using AMD (Require.js), then import it into your module:

define(["ono"], function(ono) { /* your module's code */ })

API

ono([err], [props], [message, ...])

Creates an Error object with the given properties.

• err - (optional) An existing error object. This error's message and stack trace will be appended to the new error.

• props - (optional) An object whose properties will be added to the new error. Properties can be anything, including objects and functions.

• message - (optional) The error message string. If it contains placeholders, then pass each placeholder's value as an additional parameter. See ono.formatter for more info.

Specific error types

The default ono() function always creates Error objects, but you can use any of the following methods to explicitly create the corresponding Error subclass. The method signatures are exactly the same as above.

ono.formatter

By default, Node's util.format() function is used (even in browsers) to format error messages and substitute placeholders with their corresponding values. You can set ono.formatter to a third-party formatter or even your own custom implementation, like this:

ono.formatter = function(message) {
    var params = Array.prototype.slice.call(arguments, 1);
    return params.reduce(function(message, param, index) {
        return message.replace("$" + index, param);
    }, message);
}

throw ono("$0 must be greater than $1", 4, 10);

Contributing

I welcome any contributions, enhancements, and bug-fixes. File an issue on GitHub and submit a pull request.

Building/Testing

To build/test the project locally on your computer:

1. Clone this repo
   git clone https://github.com/bigstickcarpet/ono.git

2. Install dependencies
   npm install

3. Run the build script
   npm run build

4. Run the unit tests
   npm run mocha (test in Node)
   npm run karma (test in web browsers)
   npm test (test in Node and browsers, and report code coverage)

License

Ono is 100% free and open-source, under the MIT license. Use it however you want.