How the variable in javascripts is treated on function call?

Question

If i have a function that have certain variable in it for example

  var test = 3; 

  function looper(){

     var testing = 1;
     testing += testing;

  }

  for (var i=0;i<=10,i++){

     looper();

     alert(test);

  }

if this function is been called in a loop each will get testing value as 2 or it is updating to last executed value ? beside can i get the value of test variable passed into the function or need to pass it as parameter ?

Answer 1

beside can i get the value of test variable passed into the function or need to pass it as parameter ?

Yes, try

   var test = 3; 
   function looper(testing)
   {
       testing += testing;
       return testing;
   }
   for (var i=0;i<=10,i++)
   {
       test = looper(test);
       alert(test);
   }

Answer 2

You have var testing = 1; so even if looped will be always over and over firstly instantiated to 1 .

You should move it outside of the function scope:

  var testing = 3;  // NOT "test" but "testing"!!!!!

  function looper(){
      testing += testing;
  }

  for (var i=0;i<=10,i++){
       looper();
  }

  alert(testing);   // "testing", remember?

Answer 3

The variable test is globally declared so the value 3 is displayed on alert. Where as on every call to a function looper the variable testing is created without retaining previous value and assigned a value 1 in that way the value of testing is always 2 on function call.

Answer 4

var test = 3; 
var testing = 1;

function looper(){
     testing += testing;
     return testing;
}
for (var i=0;i<=10,i++){
    test = looper();
    alert(test);
}