@anandsuresh/smart-error

smart-error

A SmartError is a wrapper around the JavaScript Error class providing a few additional fields:

• code: A unique code identifying the error
• metadata: Optional metadata useful for debugging (e.g. the arguments passed to the function that threw the error)
• cause: An optional error that is being wrapped by the SmartError

usage

const {create} = require('@anandsuresh/smart-error')

const MyError = create('MyError', {
  Unexpected: 'An unexpected error occurred.',
  BadArguments: 'One or more arguments passed were invalid.',
  TimedOut: 'A timeout occurred waiting for the operation to complete.'
})


function isOddNumber(number) {
  if (typeof number !== 'number')
    throw MyError.BadArguments(number)

  return (number % 2 === 0)
}

try {
  console.log(`isOddNumber(3) = ${isOddNumber(3)}`)
} catch (e) {
  if (e.isBadArguments) {
    console.error(`The argument $(e.metadata) is not a number!`)
  } else {
    console.error(e.toDetailedString())
  }
}

api

create(errorName, errors)

create takes 2 arguments:

• errorName: the name of the error. E.g. 'MyError'
• errors: an object mapping error codes to error messages. E.g. {Unexpected: 'An unexpected error occurred'}

The create() function creates a static function for each error code and an getter function to check if that is the specific error wrapped by the SmartError. Consider the following example:

const {create} = require('@anandsuresh/smart-error')

const MyError = create('MyError', {
  Unexpected: 'An unexpected error occurred.',
  BadArguments: 'One or more arguments passed were invalid.',
  TimedOut: 'A timeout occurred waiting for the operation to complete.'
})

The newly created MyError class will inherit from the JavaScript Error class and have the following instance properties:

• name: The name of the error, in this case 'MyError'
• code: The unique code of the error (Unexpected, BadArguments, TimedOut)
• message: A human-readable error message
• metadata: Optional metadata associated with the error (e.g. the arguments passed to the function that threw the error)
• cause: An optional error that is being wrapped by the SmartError
• stack: The stack-trace generated by the error
• isSmartError: Helper property that wraps an instanceof check to return whether or not the instance is a SmartError
• isUnexpected: Helper property that returns true if the MyError instance has the code Unexpected
• isBadArguments: Helper property that returns true if the MyError instance has the code BadArguments
• isTimedOut: Helper property that returns true if the MyError instance has the code TimedOut

MyError will also receive the following set of class methods:

• Unexpected(metadata, cause): Creates an returns an instance of MyError with the code property set to Unexpected
• BadArguments(metadata, cause): Creates an returns an instance of MyError with the code property set to BadArguments
• TimedOut(metadata, cause): Creates an returns an instance of MyError with the code property set to TimedOut