60 lines
1.5 KiB
JavaScript
60 lines
1.5 KiB
JavaScript
|
import assertString from './util/assertString';
|
||
|
|
var isin = /^[A-Z]{2}[0-9A-Z]{9}[0-9]$/; // this link details how the check digit is calculated:
|
||
|
|
// https://www.isin.org/isin-format/. it is a little bit
|
||
|
|
// odd in that it works with digits, not numbers. in order
|
||
|
|
// to make only one pass through the ISIN characters, the
|
||
|
|
// each alpha character is handled as 2 characters within
|
||
|
|
// the loop.
|
||
|
|
|
||
|
|
export default function isISIN(str) {
|
||
|
|
assertString(str);
|
||
|
|
|
||
|
|
if (!isin.test(str)) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
var _double = true;
|
||
|
|
var sum = 0; // convert values
|
||
|
|
|
||
|
|
for (var i = str.length - 2; i >= 0; i--) {
|
||
|
|
if (str[i] >= 'A' && str[i] <= 'Z') {
|
||
|
|
var value = str[i].charCodeAt(0) - 55;
|
||
|
|
var lo = value % 10;
|
||
|
|
var hi = Math.trunc(value / 10); // letters have two digits, so handle the low order
|
||
|
|
// and high order digits separately.
|
||
|
|
|
||
|
|
for (var _i = 0, _arr = [lo, hi]; _i < _arr.length; _i++) {
|
||
|
|
var digit = _arr[_i];
|
||
|
|
|
||
|
|
if (_double) {
|
||
|
|
if (digit >= 5) {
|
||
|
|
sum += 1 + (digit - 5) * 2;
|
||
|
|
} else {
|
||
|
|
sum += digit * 2;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
sum += digit;
|
||
|
|
}
|
||
|
|
|
||
|
|
_double = !_double;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
var _digit = str[i].charCodeAt(0) - '0'.charCodeAt(0);
|
||
|
|
|
||
|
|
if (_double) {
|
||
|
|
if (_digit >= 5) {
|
||
|
|
sum += 1 + (_digit - 5) * 2;
|
||
|
|
} else {
|
||
|
|
sum += _digit * 2;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
sum += _digit;
|
||
|
|
}
|
||
|
|
|
||
|
|
_double = !_double;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
var check = Math.trunc((sum + 9) / 10) * 10 - sum;
|
||
|
|
return +str[str.length - 1] === check;
|
||
|
|
}
|