#### Creating Function

Let's create a function that gets tc id as an argument

```  var checkTcNum = function(value) {
};

```

Convert id to string to break apart sub elements

```  value = value.toString();
```

Check if value contains only digits and it's length is eleven.

```  var isEleven = /^[0-9]{11}\$/.test(value);
```

For loop to concat first 10 digit of value and check if it's `modulus` equals to 11th position number

```  var totalX = 0;
for (var i = 0; i < 10; i++) {
totalX += Number(value.substr(i, 1));
}
var isRuleX = totalX % 10 === value.substr(10,1);
```

Create two variable that holds even and odd positioned numbers summed up.

```  var totalY1 = 0;
var totalY2 = 0;
```

For loop to sum up even positioned numbers

```  for (var i = 0; i < 10; i+=2) {
totalY1 += Number(value.substr(i, 1));
}
```

For loop to sum up odd positioned numbers

```  for (var i = 1; i < 10; i+=2) {
totalY2 += Number(value.substr(i, 1));
}
```

Check if (even positioned numbers summed up multiply with 7) minus (odd positioned numbers summed up) modulus of 10 equals to 10th positioned digit. And, assing it to isRuleY variable.

```  var isRuleY = ((totalY1 * 7) - totalY2) % 10 == value.substr(9,0);
return isEleven && isRuleX && isRuleY;
```

#### Live Demonstration from CodePen

See the Pen Validate TC ID with Javascript by Ömer Aslanbakan (@Aslanbakan) on CodePen.