[Vuejs]-How to format a phone number in regex using [Vue 2]

/^\+?[0-9]+$/g

• ^ asserts position at start of a line
• \+ matches the character +
• ? matches the
  previous token between zero and one times
• Match a single character present in the list [0-9]
• + matches the previous token between one and unlimited times
• $ asserts position at the end of a line
• /g Global modifier, return all matches