변수, 역할 영역 문제

var num1 = 5;
var num2 = num1;

num2 = 10;

alert(num2);    //10
alert(num1);    //5

var obj1 = new Object();
var obj2 = obj1;
obj1.name = "Leo";
alert(obj2.name);   //"Leo"

//        （  ）         
function setName(obj)   
{
    obj.name = "Leo";
    obj = new Object();
    obj.name = "Greg";
}
var person = new Object();      //          person 
setName(person);        //person            
alert(person.name);     //"Leo"。        ，      ，  person.name      "Greg" 。

var s = "Leo";
var b = true;
var i = 22;
var u;
var n = null;
var o = new Object();
var f = function(){};
var r = /\d+/;

alert(typeof s);    //String
alert(typeof b);    //Boolean
alert(typeof i);    //Number
alert(typeof u);    //undefined
alert(typeof n);    //Object
alert(typeof o);    //Object
alert(typeof f);    //function
alert(typeof r);    //Safari 5/Chrome 7-:function,IE/Firefox:object

//    
result = variable instanceof constructor

//ps:          Object   ，            Object          true

//              ，   true
alert(person instanceof Object);    //  perosn Object ？
alert(colors instanceof Array);     //  colors Array ？
alert(pattern instanceof RegExp);   //  pattern RegExp ？

//example 1
if(true)
{
    var color = "blue";
}
alert(color);   //"blue"(      c、c++ java ，color  if          )

//example 2
for(var i = 0; i < 10; i ++)
{
    doSomething(i);
}
alert(i);   //10