Example scope...

scopes.js

function logValues(head, four, five, six){
  console.log(head);
  console.log("four = " + four);
  console.log("five = " + five);
  console.log("six = "  + six );
  console.log("\n");
}

var integers = function( ){
  var four = 4;
  var five = 5;
  
  var binaries = function( ){
    var five = 101;
    var six  = 110;
    
    //#2 At this point, four is 4, five is 101 and six is 110.
    logValues("#2", four, five, six);
    
    four += five + six;
    
    //#3 At this point, four is 215, five is 101 and six is 110.
    logValues("#3", four, five, six);
  };
  
  //#1 At this point, four is 4, five is 5 and six is not defined.
  logValues("#1", four, five, (typeof six === 'undefined' ? 'undefined' : six));
  
  binaries( );
  
  //#4 At this point, four is 215, five is 5.
  logValues("#4", four, five, (typeof six === 'undefined' ? 'undefined' : six));
};

integers( );