Simple JS function. Returns true or false if the giving string passes Luhn Algorithm requirements.

luhn.js

<script>
  var luhnNo = '79927398711';
	
	function luhn(num){
		var numArr = num.split(''),
			tempInt, 
			odd  = 0,
			even = 0;
		
		numArr.reverse();

		for (var i = 0; i < numArr.length; i++) {
			if (i % 2 != 0) {
				//even
				tempInt = parseInt(numArr[i], 10) * 2;

				var y;
				if (tempInt<9) {
					even += parseInt(tempInt, 10);
				}else{
					var  x = '' + tempInt;
					even += parseInt(x.charAt(0), 10) + parseInt(x.charAt(1), 10);
				}
			}else{
				//odd
				odd += parseInt(numArr[i], 10);
			}
		};

		return (odd + even) % 10 ? true : false;
	}

	console.log(luhn(luhnNo));
</script>