I am assuming you mean it this way:

//global variable
var a = 10;

function SomeFunction()
{
   //changing global variable
   a = 20;

   //local variable
   var b = 20;
}

In this case, the local and global variables both have page scope. Even if
you place these variables into files, they only exist as long as the page is
accessed.

So, yes, each user gets his own global variables.

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