window.num = 22;
var o = {num: 11};
function sayNum(){
  alert(this.num)
}
sayNum();//22
o.sayNum = sayNum;
o.sayNum();//11

function fn1(){
  console.log(this);
}

fn1();

function Person(name){
  this.name = name;
}
Person.prototype.printName = function(){
  alert(this.name);//Byron
};

var p1 = new Person('Byron');

var obj1 = {
  name: 'Byron',
  fn : function(){
    console.log(this);
  }
};

obj1.fn();

window.color = 'red';
var o = {color: 'blue'};
function sayColor(){
  alert(this.color);
}
sayColor.call(this);//red
sayColor.call(window);//red
sayColor.call(o);//blue

function fn(){
   console.log(this)//windwow
   function InnerFn(){
     console.log(this)
   }
   InnerFn.call(this)//window
}
fn();
 function fn0(){
   console.log(this)//window
}
function fn1(){
   fn0.call(this);
   console.log(this);//window
}
fn1();
function fn0(){
 console.log(this)//object
}
var o = {
  fn1: function fn1(){
    fn0.call(this);
    console.log(this);//object
  }
}
o.fn1();  

window.color = 'red';
var o = {color : 'blue'};
function sayColor(){
  alert(this.color)
}
var objectSayColor = sayColor.bind(o);
objectSayColor();//blue

var a = 1;
function fn(num1,num2){
  var b = 2;
  function fnInner(){
    var c = 3;
    alert(a + b + c);
  }
  fnInner();//fnInner调用时局部执行环境创建
}
fn(4,5);//fn调用时局部执行环境创建

var scope = 'global scope';
function checkscope(){
  var scope = 'local scope';
  function f(){return scope};
  return f;
}
checkscope()();//local scope

var num1 = 1;
function Outer(){
  var num2 = 2;
  console.log(num1 + num2);//3
  function Inner(){
    //这里可以访问num3,num2,num1
    var num3 = 3;
    console.log(num1 + num2 + num3);//6
    }
  //这里可以访问num2,Inner(),num1但不能访问num3
  Inner();
}
Outer();
console.log(num1);//1，执行环境
//这里只能访问num1

 var name = 'Byron';
  function fn(){
    var name = 'Csper';
    console.log(name);//Casper
  }
  fn();

var a = 1;
function prison (a) {
  console.log(a);//1
  var a;
  console.log(a);//1
}
prison(1);

alert(typeof fn);//function，函数声明提前
alert(typeof fn0);//undefined,变量声明提前但未赋值
function fn(){
//函数表达式
}
var fn0 = function(){
//函数定义式
}
alert(typeof fn0);//function，此时变量已被赋值