get Attribute 把它插入到我的 src ??，我不知道太多帮助我

Question

我得到的结果"undefined"：

代码 js:

document.getElementById("myImg").src = "hackanm"+x+".gif";
var x = document.getElementsByTagName("img")[0].getAttribute("data");

HTML:

<img data="WhatIWantToAdd" id="myImg" src="" >

Answer 1

顺序错误。即使声明了 x，它的值也会在赋值之前使用。因此未定义

var x = document.getElementsByTagName("img")[0].getAttribute("data");
document.getElementById("myImg").src = "hackanm"+x+".gif";

<img data="WhatIWantToAdd" id="myImg" src="" >

get Attribute to insert it in my src ??, I do not know too much help me