why “11”-1 is not changed to “1” in line 5
At 1 hour 36 minute in webinar JS 1
When JS sees “11”+1 it converts the 1 into a string and concatenates. On the other hand - is only an arithmetic operator, so JS converts both operands into numbers before applying the operator. Because + is meant for addition and also for concatenating strings, - is only used for subtraction.