Javascript Substring() Returning The Wrong Value From My String?

I have this code:

var sequence = $stateParams.testId.length == 14 ?
               parseInt($stateParams.testId.substring(11, 2)) : 0;

What I expect is for the sequence to be set to 01 (the last two numbers). But what happens is that it returns 198.

Can someone explain why this is?

console.log($stateParams.testId) // "01198-05282-01"

console.log(sequence) // 198

String#substring works with the indexes.

The signature of the substring is

str.substring(indexStart[, indexEnd])

Note that the second parameter is the index itself and not the length of the substring.

^{Quoting from MDN}

If indexStart is greater than indexEnd, then the effect of substring() is as if the two arguments were swapped; for example, str.substring(1, 0) == str.substring(0, 1).

So,

.substring(11, 2) is equivalent to .substring(11, 2) which will give the substring "198-05282-" and using parseInt() on it will give the output as 198.

1. Use the second param as index, here, 14(12 + 2)
2. Use the radix parameter to parseInt as 10 to avoid unexpected results

Code:

var str = '01198-05282-01';

var sequence = str.length == 14 ?
    parseInt(str.substring(12, 14), 10) : 0;
//                             ^^   ^^

console.log(sequence);

To get the substring using the length, use String#substr

str.substr(12, 2)