function set(){
    var items={}
    this.has=function(value){
        return items.hasOwnProperty(value)
    }
    this.add=function(value){
        if(!this.has(value)){
            items[value]=value
        
            return true
        }else{
            return false
        }
    }
    this.remove=function(value){
       if(this.has(value)){
        delete items[value]
        return true
       }else{
        return false
       }

    }
    this.clear=function(){
        items={}
    }
    this.size=function(){
          var count=0
          for(var prop in items){ 
            if(this.has(prop)){   //因为对象圆形还包含别的自带继承属性 用has保险 
                ++count
            }
          }
         return count
    }
    this.values=function(){
        var keys=[]
        for(var prop in items){
            if(this.has(prop)){
                keys.push(prop)
            }
        }
        return keys
    }
    this.union=function(otherSet){  //合集
        var unionSet=new set()
        var values=this.values();
        for(var i=0;i<values.length;i++){
            unionSet.add(values[i])
        }

        var values=otherSet.values();
        for(var i=0;i<values.length;i++){
            unionSet.add(values[i])
        }
        return unionSet
     }
     this.intersection=function(otherSet){  //交集
           var intersectionSet=new set()
           var values=this.values()
           for(var i=0;i<values.length;i++){
                if(otherSet.has(values[i])){
                    intersectionSet.add(values[i])
                }

           }
           return intersectionSet
     }
    this.unintersection=function(otherSet){  //差集
           var intersectionSet=new set()
           var values=this.values()
           for(var i=0;i<values.length;i++){
                if(!otherSet.has(values[i])){
                    intersectionSet.add(values[i])
                }

           }
           return intersectionSet
     }
     this.son=function(otherSet){    //子集
        if(this.size()>otherSet.size()){
            return false
        }else{
             var values=this.values()
             for(var i=0;i<values.length;i++){
                if(!otherSet.has(values[i])){
                    return false
                }
             }
             return true

        }

     }
}

 var see=new set()
 see.add(1)
 see.add(2)


var see2=new set()
see2.add(1)
see2.add(5)
see2.add(7)


var see3=new set()
see3.add(5)

var ab=see.union(see2)
console.log(ab.values())
var cb=see.intersection(see2)
console.log(cb.values())

var cj=see.unintersection(see2)
console.log(cj.values())


console.log(see3.son(see))
console.log(see3.son(see2))