看犀牛书小结(2)

function GenericToString(x,y){
     this.x = x;

     this.y = y;

     this.getX = function(){return this.x;}

     this.getY = function(){return this.y;}

}

 

GenericToString.prototype.toString = function(){
var props = [];

for(var name in this){

if(!this.hasOwnProperty(name))continue;

var value = this[name];

var s = name + ":";

switch(typeof value){

    case 'function':

    s+="function";

    break;

case 'object':

    if(value instanceof Array) s+="Array";

    else s+value.toString();

    break;

default:

    s+=String(value);

    break;

}

props.push(s);

}

return "(" + props.join(", ") + ")";

}

 

GenericToString.prototype.equals = function(that){

    if(this == that) return true;

    var propsInThat = 0;

    for(var name in that){

        propsInThat++;

        if(this[name] != that[name]) return false;

    }

 

    var propsInThis = 0;

    for(name in this) propsInThis++;

    if(propsInThat != propsInThis) return false;

   

    return true;

}

 

var g = new GenericToString(1,2);

for(var gname in g){

    if(!g.hasOwnProperty(gname)){

        document.write(gname + "<br>");   

    }

}

document.write("toString方法-->"+g.toString());

 

上面的输出结果是：

equals
toString方法-->(x:1, y:2, getX:function, getY:function)

 

疑问：GenericToString对象的原型prototype里面不是有toString方法和equals方法的？

怎么用hasOwnProperty()方法的时候toString()方法却不在里面，但是用对象调用toString方法的

时候却用上了这个方法？