IndexOf

Back to a variable. Also this time there is a lot of text:

let a = 0;

a = a - "Strings can help to increment our variable with this number:".indexOf('1') // a = 1

Explanation

This one doesn’t have tricky JS code. We just try to find index of 1 in string, but it will return -1 because this substring isn’t present. After that simple math helps us to increment variable.