js深入研究之函数内的函数

function foo() {
  var a = 10;
 
  function bar() {
    a *= 2;
  }
   
  bar(); 
  return a;
}

function foo() {
  var a = 10;
 
  function bar() {
    a *= 2;
    return a;
  }
   
  return bar;      
}

var baz = foo(); // baz is now a reference to function bar.
alert(baz()); // returns 20.
alert(baz()); // returns 40.
alert(baz()); // returns 80.

var blat = foo(); // blat is another reference to bar.
alert(blat()); // returns 20, because a new copy of a is being used.