怎么遍历对象属性并返回值

如何遍历对象属性并返回值？
如有对象
a = {
         name:"text",
         childrenElm:{
                   parentID:0,
                   myName:"john",
                   aihao:{
                            web:"html",
                             code:"js"
                    }
          }
}

我想通过一个方法  getAttrVal(attrName)  直接取得该属性的值
下面是刚才编写的，但是不能达到预期的效果,这写法会输出N次。

alert(getAttrVal("code"))


function getAttrVay(attrName)

{

	var obj = a;

        for(var i in obj){

		if(typeof(obj[i]) == "object" && obj[i] !== null){				

					getAttrVay(obj[i],attrName)				

		}else{

			if (i == attrName){				

					return obj[i];				

				break;

			}	

		}	

	}

}

------解决方案--------------------

a = {

         name:"text",

         childrenElm:{

                   parentID:0,

                   myName:"john",

                   aihao:{

                            web:"html",

                             code:"js"

                    }

          }

}


alert(getAttrVay(a, "code"))

 

function getAttrVay(obj, attrName)

{

   for(var i in obj){

     if(typeof(obj[i]) == "object" && obj[i] !== null){                

       return getAttrVay(obj[i],attrName)