js 作用域的问题

//a(); //is not a function
var a=function(){
console.log("111");
}
a(); //111

b(); //222
function b(){
console.log("222");
}

console.log(params.name);
var params={
name: "xiaoming"
}
console.log(params.name); //xiaoming

var F=function(){};
Object.prototype.a=function(){};
Function.prototype.b=function(){};
var f=new F();
console.log(f.a); //function (){}
console.log(f.b); //undefined

var a={n:1};
var b=a;
a.x=a={n:2};
console.log(a.x); //undefined
console.log(b.x); //Object {n: 2}