Why is undefined displayed instead of a space?

Question

JavaScript

function calculate(){
var str=document.getElementById("vvodA").value;

var i=0;
var s=new String(s);
var s1=new String(s1);
while (i<str.length)

{
  if (str.charAt(i)!=' ') {
    s+=str.charAt(i);
    i++;
    }
  else 
  {
    i++;
    s1=s;
    s=' ';
  }
  
}
s=s.concat(s1);
alert(s);
}

Answer 1

var s=new String(s);
var s1=new String(s1);
it's not easier to do this:
var s= "",
s1= "";
I don't know what this new String is but I can assume that it should be like this var s1=new String("s1");

Answer 2

Well, at least bring your code, for the sake of decency and so as not to be telepaths)
It is obvious that you are clearly “shove something wrong” in this line)