js实现接口的几种方式

Javascript模仿接口可以有三种方式：1.注释法 2.检查属性法 3.鸭式辨形法 

1.注释法:此方法属于程序文档范畴，对接口的继承实现完全依靠程序员自觉

/*
   interface People{
         function createHead();
         function createBody();
   }
*/
var woman = function(name){   //implements People interface
    this.name = name;
}
woman.prototype.showName = function(){
    alert(this.name);
}
woman.prototype.createBody = function(){  //实现必要的方法
    alert("身体已经创建好");
}
woman.prototype.createHead = function(){
    alert("头部已经创建好");
}

//2.属性检查法：把要实现的接口方法添加到类属性列表里，通过定义好的检测反复检查是否已经实现了那些方法
//优缺点：可以强迫程序员实现接口，没实现就报错。不过虽然声明了自己实现了哪些方法，但实现时很可能有遗漏

/*
interface People{
    function createHead();
    function createBody();
}
*/
var woman = function(name){
    this.name = name;
    this.implementsInterfaces = ['People'];
}
woman.prototype.showName = function(){
    alert(this.name);
}
woman.prototype.createBody = function(){  //实现必要的方法
    alert("身体已经创建好");
}
woman.prototype.createHead = function(){
    alert("头部已经创建好");
}

function implement(obj,interfaces){
    for(var i=1;i<interfaces.length;i++){
        var interfaceName = interfaces[i];
        var interfaceFound = false;
        for(var j=0;j<obj.implementsInterfaces.length;j++){
            if(obj.implementsInterfaces[j] = interfaceName){
                 interfaceFound = true;
                 break;
            }
        }
        if(!interfaceFound){
              return false;
        }
    }
    return true;
}

function  isImplememts(instance,interfaces){    //判断对象是否已经继承相应接口
    if(!implement(instance,interfaces)){
        throw new Error("Object doesn't implement a required interface");
    }
}

3.鸭式辨型法：（不通过外表判断鸭子，而通过其是否有鸭子的特性来判断。如James Whitcomb Riley所说，像鸭子一样走路并且嘎嘎叫的就是鸭子）
上面俩种都声明了自己实现了那些接口，其实声明不重要，实现接口核心的是类实现了接口方法集。如果类具有了接口定义的所有方法函数名相同的函数，那么认为它实现了接口

//接口类，用来创建接口
var Interface = function(name,motheds){
    if(agruments.length!=2){
        throw new Error("Interface constructor called with "+arguments.length+"arguments,but expected exactly 2");
    }
    this.name = name;
    this.methods = [];
    for(var i=0;i<motheds.length;i++){
        if(typeof motheds[i] !== 'string'){
            throw new Error('Interface constructor expects mothed names to be'+'passes in as a string');
        }
        this.methods.push(motheds[i]);
    }
}
Interface.prototype.ensureImplements = function(objs){
    if(agruments.length != 1){
        throw new Error("Interface constructor called with "+arguments.length+"arguments,but expected exactly 1")
    }
    for(var i=0;i<objs.length;i++){
         var obj = objs[i];
         for(var j=0;j<this.motheds.length;j++){
               var mothed = this.methods[j];
               if(!obj[mothed] || !typeof obj[mothed] !== 'function'){
                    throw new Error('Function Interface.ensureImplements:implements interface'+this.name+',obj.mothed'+mothed+'was not found');
               }
         }
    }
}
//创建接口
var People = new Interface('People',['createHead','createBody']);
//子类
var Woman = function(name){
    this.name = name;
    this.implementsInterfaces = ['People'];
}
Woman.prototype.showName = function(){
    alert(this.name);
}
Woman.prototype.createBody = function(){  //实现必要的方法
    alert("女人身体已经创建好");
}
Woman.prototype.createHead = function(){
    alert("女人头部已经创建好");
}
//子类
var Man = function(name){
    this.name = name;
    this.implementsInterfaces = ['People'];
}
Man.prototype.showName = function(){
    alert(this.name);
}
Man.prototype.createBody = function(){  //实现必要的方法
    alert("男人身体已经创建好");
}
Man.prototype.createHead = function(){
    alert("男人头部已经创建好");
}
//判断是否实现
Poeple.ensureImplements(['Woman','Man']);