密码框问题

当你写入密码的时候，希望输入的密码不是明文的那么就需要下面的代码

var tx = document.getElementByIdx_x("tx"),pwd = document.getElementByIdx_x("pwd");

tx.onfocus = function(){

  if(this.value != "密码") return;

  this.style.display = "none";

  pwd.style.display = "";

  pwd.value = "";

  pwd.focus();

}

pwd.onblur = function(){

  if(this.value != "") return;

  this.style.display = "none";

  tx.style.display = "";

  tx.value = "密码";

}