getCheckCode(id)

Calculate the check digit (last digit) of an ID number.

Signature

function getCheckCode(id: string): string | null

Parameters

Parameter	Type	Description
id	string	ID number (first 17 digits)

Returns

Returns the computed check digit (0-9 or X). Returns null if the input format is invalid.

Live Demo

Example

import { getCheckCode } from 'china-id-card'

getCheckCode('62292219780811849')  // → '8'
getCheckCode('31000019810227632')  // → '3'