Default argument values in JavaScript functions [duplicate]

Answer 1

I have never seen it done that way in JavaScript. If you want a function with optional parameters that get assigned default values if the parameters are omitted, here's a way to do it:

 function(a, b) {
      if (typeof a == "undefined") {
        a = 10;
      }

      if (typeof b == "undefined") {
        a = 20;
      }

      alert("a: " + a + " b: " + b);
    }