2. this 指向

1、 阅读代码

function foo() {
  console.log( this.a );
}
function doFoo() {
  foo();
}
var obj = {
  a: 1,
  doFoo: doFoo
};
var a = 2; 
obj.doFoo()

2、 阅读代码

var a = 10
var obj = {
  a: 20,
  say: () => {
    console.log(this.a)
  }
}
obj.say() 
var anotherObj = { a: 30 } 
obj.say.apply(anotherObj)

3、 阅读代码

function a() {
  console.log(this);
}
a.call(null);

4、 阅读代码

var obj = {
   say: function() {
     var f1 = () =>  {
       console.log("1111", this);
     }
     f1();
   },
   pro: {
     getPro:() =>  {
        console.log(this);
     }
   }
}
var o = obj.say;
o();
obj.say();
obj.pro.getPro();

5、 阅读代码

var myObject = {
    foo: "bar",
    func: function() {
        var self = this;
        console.log(this.foo);  
        console.log(self.foo);  
        (function() {
            console.log(this.foo);  
            console.log(self.foo);  
        }());
    }
};
myObject.func();

6、 阅读代码

window.number = 2;
var obj = {
 number: 3,
 db1: (function(){
   console.log(this);
   this.number *= 4;
   return function(){
     console.log(this);
     this.number *= 5;
   }
 })()
}
var db1 = obj.db1;
db1();
obj.db1();
console.log(obj.number);     
console.log(window.number);

7、 阅读代码

var length = 10;
function fn() {
    console.log(this.length);
}
var obj = {
  length: 5,
  method: function(fn) {
    fn();
    arguments[0]();
  }
};
obj.method(fn, 1);

8、 阅读代码

var a = 1;
function printA(){
  console.log(this.a);
}
var obj={
  a:2,
  foo:printA,
  bar:function(){
    printA();
  }
}
obj.foo();
obj.bar(); 
var foo = obj.foo;
foo();

9、 阅读代码

var x = 3;
var y = 4;
var obj = {
    x: 1,
    y: 6,
    getX: function() {
        var x = 5;
        return function() {
            return this.x;
        }();
    },
    getY: function() {
        var y = 7;
        return this.y;
    }
}
console.log(obj.getX()) 
console.log(obj.getY())

10、 阅读代码

var a = 10; 
 var obt = { 
   a: 20, 
   fn: function(){ 
     var a = 30; 
     console.log(this.a)
   } 
 }
 obt.fn();  
 obt.fn.call(); 
 (obt.fn)();

11、 阅读代码

function a(xx){
  this.x = xx;
  return this
};
var x = a(5);
var y = a(6);
console.log(x.x) 
console.log(y.x)

12、 阅读代码

function foo(something){
    this.a = something
}
var obj1 = {
    foo: foo
}
var obj2 = {}
obj1.foo(2); 
console.log(obj1.a);
obj1.foo.call(obj2, 3);
console.log(obj2.a);
var bar = new obj1.foo(4)
console.log(obj1.a);
console.log(bar.a);

13、 阅读代码

function foo(something){
    this.a = something
}
var obj1 = {}
var bar = foo.bind(obj1);
bar(2);
console.log(obj1.a);
var baz = new bar(3);
console.log(obj1.a);
console.log(baz.a);