freeCodeCamp/curriculum/challenges/espanol/10-coding-interview-prep/rosetta-code/cusip.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
5a23c84252665b21eecc7e05	CUSIP	5	302241	cusip

--description--

A CUSIP is a nine-character alphanumeric code that identifies a North American financial security for the purposes of facilitating clearing and settlement of trades. The CUSIP was adopted as an American National Standard under Accredited Standards X9.6.

--instructions--

Write a function that takes a string as a parameter and checks if the string is valid CUSIP.

--hints--

isCusip should be a function.

assert(typeof isCusip == 'function');

isCusip("037833100") should return a boolean.

assert(typeof isCusip('037833100') == 'boolean');

isCusip("037833100") should return true.

assert.equal(isCusip('037833100'), true);

isCusip("17275R102") should return true.

assert.equal(isCusip('17275R102'), true);

isCusip("38259P50a") should return false.

assert.equal(isCusip('38259P50a'), false);

isCusip("38259P508") should return true.

assert.equal(isCusip('38259P508'), true);

isCusip("38259P50#") should return false.

assert.equal(isCusip('38259P50#'), false);

isCusip("68389X105") should return true.

assert.equal(isCusip('68389X105'), true);

isCusip("68389X106") should return false.

assert.equal(isCusip('68389X106'), false);

isCusip("5949181") should return false.

assert.equal(isCusip('5949181'), false);

--seed--

--seed-contents--

function isCusip(s) {

}

--solutions--

function isCusip(s) {
  if (s.length != 9) return false;
  var sum = 0;
  var ASCII = x => x.charCodeAt(0);
  for (var i = 0; i < 7; i++) {
    var c = s.charCodeAt(i);

    var v;
    if (c >= ASCII('0') && c <= ASCII('9')) {
      v = c - 48;
    } else if (c >= ASCII('A') && c <= ASCII('Z')) {
      v = c - 64; // lower case letters apparently invalid
    } else if (c == ASCII('*')) {
      v = 36;
    } else if (c == ASCII('@')) {
      v = 37;
    } else if (c == ASCII('#')) {
      v = 38;
    } else {
      return false;
    }
    if (i % 2 == 1) v *= 2; // check if odd as using 0-based indexing
    sum += Math.floor(v / 10) + (v % 10);
  }
  return s.charCodeAt(8) - 48 == (10 - (sum % 10)) % 10;
}