Question

I want to know if these two scripts do the same thing:

parseInt(num)?num=parseInt(num):num=str.length

and

num=parseInt(num)||str.length;

And in case they are not, I need to know what the second do.

Answer 1

Yes they are same with later (short circuit evaluation) being terse and a beauty of JS (or other languages that support it):

num = parseInt(num) || str.length;

Both in turn are short-cut of this:

if (parseInt(num)){
   num = parseInt(num);
}
else {
   num = str.length;
}

Good Practices:

• Don’t foget var keyword before num variable otherwise it goes into global scope.
• Always specify a base to parseInt eg parseInt(num, 10) unless otherwise needed

---

Readings:

• Short-Circuit Evaluation
• Ternary Operator