this 不同情况指代的对象

this.a = 10;
alert(a);//10

b = 20;
alert(this.b);//20

var c = 30;
alert(this.c);//30

var a = 10;
var bar = {
    a: 20,
    test: function(){
        alert(this.a);
    }
}
bar.test();//20

var a = 10;
function foo(){
    alert(this.a);
}
foo();//10

var a = 10;
var foo = {
    a: 20,
    fn: (function(){
        alert(this.a);
    })()
}
foo.fn//10

var a = 10;
var oTimer1 = setInterval(function(){
    var a = 20;
    alert(this.a);//10
    clearInterval(oTimer1);
},100);

(function(){
    eval("alert(this)");//[object Window]
})();
function Foo(){
    this.bar = function(){
        eval("alert(this)");//[object Object]
    }
}
var foo = new Foo();
foo.bar();

function Person(name,age){
    this.name = name;
    this.age = age;
    this.sayName = function(){
        alert(this.name);
    }
}
var p1 = new Person(‘lily‘,‘20‘);
p1.sayName();//‘lily‘