Custom replace function for JSON.stringify to stringify JS Error Objects.

error-stringify.js

jsonFriendlyErrorReplacer = (key, value) => {
  if (value instanceof Error) {
    value = Object.assign({}, 
      value, // Pull all enumerable properties, supporting properties on custom Errors
      {      // Explicitly pull Error's non-enumerable properties
        name: value.name, 
        message: value.message, 
        stack: value.stack
      }
    )
  }
  return value
}

let obj = {
  error: new Error('nested error message')
}

console.log('Result WITHOUT custom replacer:', JSON.stringify(obj))
console.log('Result WITH custom replacer:', JSON.stringify(obj, jsonFriendlyErrorReplacer, 2))