https://repl.it/CuhM/0 created by selmanon

closure.js

var level1 = "a";

function outer() {
  var level2 = "b";  
  function middle() {
    var level3 = "c";    
    // the function 'inner' can access all variables in the outer scopes
    function inner() {
      document.write (level1 + level2 + level3);
    }
    inner();
  }
  middle();
}

outer();
  
  

CuhM-0_console_dump.txt

Native Browser JavaScript
>>> abc
=> undefined