$(document).ready(function(){ 
 var doc=document,
 inputs=doc.getElementsByTagName('input'),
 supportPlaceholder='placeholder'in doc.createElement('input'),
 
 placeholder=function(input){
  var text=input.getAttribute('placeholder'),
  defaultValue=input.defaultValue;
  if(defaultValue==''){
  input.value=text
  }
  input.onfocus=function(){
  if(input.value===text)
  {
   this.value=''
  }
  };
  input.onblur=function(){
  if(input.value===''){
   this.value=text
  }
  }
 };
 
 if(!supportPlaceholder){
  for(var i=0,len=inputs.length;i<len;i++){
   var input=inputs[i],
   text=input.getAttribute('placeholder');
   if(input.type==='text'&&text){
    placeholder(input)
   }
  }
 }
 });

<input type="text" placeholder="输入商品编码" name="goodscode" id="goodscode" value="123" />
<input type="text" placeholder="输入商品名称" name="goodsname" id="goodsname" value="输入商品名称" />