js接口的实现

// Interface Constructor
var Interface=function(name,methods){
  if(arguments.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,len = methods.length;i < len;i++){
    if(typeof methods[i] !== 'string'){
      throw new Error("Interface constructor expects method names to be "+"passed in as a string.");
    }
    this.methods.push(methods[i]);
  }
};

// Static class method.
Interface.ensureImplements = function(obj){
  if(arguments.length<2){
    throw new Error("Function Interface.ensureImplements called with "+arguments.length+"arguments,but expected at least 2.");
  }
  for(var i = 1,len =arguments.length;i <len;i++){
    var interface=arguments[i];
    if(interface.constructor !== Interface){
      throw new Error("Function Interface.ensureImplements expects arguments two and above to be instances of Interface.");
    }

    for(var j =0,methodsLen=interface.methods.length;j < methodsLen;j++){
      var method=interface.methods[j];
      if(!obj[method] || typeof obj[method] != 'function'){
        throw new Error("Function Interface.ensureImplements: object "+
        "does not implement the "+interface.name+" interface.Method"+
        method+" was not found.");
      }
    }
  }
};

 

采用注释法和鸭式辨型法相结合的方式

//Interfaces
var Composite = new Interface('Composite',['add','remove','getChild']);
var FormItem = new Interface('FormItem',['save']);

//CompositeForm class
var CompositeForm = function(id,method,action){//implements Composite,FormItem
  ...
}
...