javascript-opentimestamps/src/extend-error.js

JS Porting of OpenTimestamps

var util = require('util')
var assert = require('assert')

/**
 * Add extend() method to Error type
 *
 * @param subTypeName
 * @param errorCode [optional]
 * @returns {SubType}
 */

Error.extend = function (subTypeName, errorCode /* optional */) {
  assert(subTypeName, 'subTypeName is required')

  // define new error type

  var SubType = function (message) {
    // handle constructor call without 'new'
    if (!(this instanceof SubType)) {
      return new SubType(message)
    }

    // include stack trace in error object
    try {
      Error.captureStackTrace(this, this.constructor)
    } catch (err) {}

    // populate error details
    this.name = subTypeName
    this.code = errorCode
    this.message = message || ''

    // fix the error message in trace
    this.stack = this.stack.replace('Error', this.toString())
  }

  // inherit the base prototype chain
  util.inherits(SubType, this)

  // override the toString method to error type name and inspected message (to expand objects)
  SubType.prototype.toString = function () {
    return this.name + ': ' + util.inspect(this.message)
  }

  // attach extend() to the SubType to make it extendable further
  SubType.extend = this.extend

  return SubType
}