Question

I’ve read some questions here about this:

1. This is good

   function(a, b) {
       a = (typeof a === 'undefined')? 'default_val' : a;
       b = (typeof b === 'undefined')? 'default_val' : b;
   }
   

2. This is somewhat troublesome (works for anything but boolean values)

   function(a, b) {
       a = a || 'default_val';
       b = b || 'default_val';
   }
   

   If you pass false it break the logic. So this should be marked as a bad habit

3. There were a few question, but I have never seen the answer to this (nobody answered directly to the question): is this (last method) good (does anyone sees any issues with it) ?

   function(a = 'default_val', b = 'default_val') {
       // your code
   }
   

I have tested this 3th method but couldn’t find any issues. I would like the last method. It is more cleaner and looks more like the structure of other languages.

Thanks

Answer 1

The third example is syntactically incorrect in the most of the modern browsers. Currently it would work in FireFox only (here is a fixed issue), since this syntax is a part of not yet approved ECMAScript Harmony standard.