类：类与对象字面量和接口差不多，比较两个类类型的对象时，只有实例的成员会被比较。 静态成员和构造函数不在比较的范围内。class Animal {    feet: number;    constructor(name: string, numFeet: number) {}}class Size {    feet: number;    constructor(numFeet: number) { }}let a: Animal = new Size(1); //冒号后面仅仅只是检验属性是不是一样的，不是类型let s: Size = new Animal("",0);function creat(x:Animal){} //冒号只是检验属性，不做类型检查，creat(a);creat(s);console.log(a);//Size {}console.log(s);//Animal {}-----------------------------------------------------------交叉类型：class A{    constructor(public _a1:number,public _a2:number){        this._a1 = _a1;        this._a2 = _a2;    }    fa1(){}}interface b{    b1:number;    f1();}class B implements b{    b1:number;    f1(){        console.log("f1");    }    fb1(){}    constructor(b1:number,public _B1:number,public _B2:number){        this.b1 = b1;        this._B1 = _B1;        this._B2 = _B2;    }}var a = new A(0,2);a._a1 = 1;var b = new B(3,4,5);console.log(a);for(let i in a){    console.log(i + "--" + typeof i);}console.log(b);for(let i in b){    console.log(i + "----" + typeof i);}var result;function extend
     
      (a : T, b : U): T & U {    result = 
      
       {};    for(let i in a){        //(
       
        result)[i] = (
        
         a)[i];        //result[i] = a[i];        (
         
          result)[i] = (
          
           a)[i]; } for(let i in b){ if(!result.hasOwnProperty(i)){ // (
           
            result)[i] = (
            
             b)[i]; result[i] = b[i]; (
             
              result)[i] = (
              
               b)[i]; } } return result;}extend(a,b);console.log("-----------------");console.log(result);for(let i in result){ console.log(i + "----" + typeof i);}