babel-plugin-transform-fake-error-class

babel-plugin-transform-fake-error-class

If you want to create your own error types, extending Error is the best way to do that:

class MyError extends Error {
  constructor(message) {
    super(message)
    this.name = 'MyError'
  }
}

Unfortunately, this doesn't work in old ES5 environments, and Babel's built-in class transforms don't always give good stack traces.

Since extending the built-in Error object doesn't always work, this plugin doesn't do that. Instead, it transforms the above class into something like this:

function MyError(message) {
  var _this = new Error(message)
  _this.name = 'MyError'
  return _this
}

This works almost perfectly in both old and new environments. You still call new MyError(), just as before, properties like name appear as they should, and stack traces look perfect, but under the hood this is no longer a class. That means instanceof MyError will always return false, but that's the only major downside.

This plugin also supports methods and class properties, including static ones:

class MyError extends Error {
  name = 'MyError'

  static isMyError(error) {
    return error.constructor === MyError
  }

  getReason() {
    return this.message
  }
}

Installing

npm install --save-dev babel-plugin-transform-fake-error-class
# or
yarn add --dev babel-plugin-transform-fake-error-class

Now add this plugin to your .babelrc:

{
  "plugins": [
    "babel-plugin-transform-fake-error-class"
  ]
}