Question

This is my code:

function func(){
 for(i=0; i < 5; i++){
   alert('B');
 }
}

for(i=0; i < 5; i++){
  func();
  alert('A');
}

What I expected was: BBBBBABBBBBABBBBBABBBBBABBBBBA

but what received was just BBBBBA

I found out that’s because there is function scope, not block scope in JS. What I’d like to know is how to preserve such a behavior. I mean to force something like block scope. Otherwise it’s very easy to make really nasty bugs – e.g. while using a function somebody else wrote or the one you wrote yourself, but a few months earlier.

Answer 1

Make sure you use var i=0 instead of just i=0. Otherwise, it floats into the global scope and gets used by both loops.

function func(){
    for(var i=0; i < 5; i++){
       alert('B');
    }
}

for(var i=0; i < 5; i++){
    func();
    alert('A');
}