Lexical vs. Dynamic Scope

lex_v_dyanamic

// Lexical 

(function(){
  function addIt(){
    var x = 100;
    
    function addInside(){
      return x += 5;
    }
    
    return addInside();
  }
  
  console.log(addIt());
}());


// Dyanamic
(function(){
  function addDynamic(){
    return x += 5;
  }
  
  function dynamic1(){
    var x = 1;
    return addDynamic();
  }
  
  function dynamic2(){
    var x = 100;
    return addDynamic();
  }
  
  // This will fail unless we make a global to this closure, of x
  // dynamic1();
  // dynamic2();
  
  var x = 100;
  console.log(dynamic1()); // 105
  console.log(dynamic2()); // 110 because x is incremented by dynamic1
}());