js构造函数创建对象是否加new问题

function Obj(name){
// TO DO
}
obj. /* TO DO */ = "name2";
var a = Obj("name1");
var b = new Obj;

function Obj(name){
this.name = name;
console.log(this); // 严格模式下是undefined 非严格模式下是window对象
}
var a = Obj("name1");
console.log(a); // 结果 => undefined

function Obj(name){
this.name = name;
}
var b = new Obj;
console.log(b); // Obj { name: undefined }
function Obj(name){
this.name = name;
return 'chic';
}
var b = new Obj;
console.log(b); // 同上

function Obj(name){
this.name = name;
return {};
}
var b = new Obj;
console.log(b); // {}

function Obj(name){
this.name = name;
return this;
}
Obj.prototype.name = "name2";
var a = Obj("name1");
var b = new Obj;