Checks the validity of a given Isracard credit card number

isracard.js

/*License: MIT*/
function isracardCheck(num) {//algorithm explanation: https://web.archive.org/web/20140227235803/http://povolotski.me/2013/09/24/isracard-credit-card-number-validation-2/
	if(typeof num !== 'number') num=''+num;
	if(num.length < 8 || num.length > 9) return false;
	var sum=0;
	num.split('').forEach(function(val,key){
		sum+=parseInt(val,10)*(num.length-key);
		})
	return sum % 11 == 0;
	}

A bit more modern code.

function validateIsracard(value) {
  const num = String(value);
  if (num.length < 8 || num.length > 9) {
    return false;
  }
  const sum = Array.from(num, Number).reduce(
    (sum, val, index) => sum + val * (num.length - index),
    0
  );

  return sum % 11 === 0;
}