user.js

/**

• Created by Administrator on 2018/10/16.
  */
  window.onload=function(){
  var o_username=document.getElementById("username");
  var o_password=document.getElementById("password");
  o_username.onfocus=function () {
  o_username.setAttribute("style","background-image:none;");
  }
  o_username.onblur=function () {
  o_username.setAttribute("style","background-image: url('img/b.jpg')");
  }

  o_password.onfocus=function () {
  o_password.setAttribute("style","background-image:none;");
  }
  o_password.onblur=function () {
  o_password.setAttribute("style","background-image: url('img/c.jpg')");
  }
  }