您需要访问输入字段的value以获取要比较的适当文本值。此外，您的逻辑应该先检查空值，然后检查错误。

var pw = "1234";

function checkpw(event, input) {
  var x = document.getElementById("pw"); // could be `input` instead
  
  if (x.value === "") {
    console.log("no password entered");
  } else if (x.value !== pw) {
    console.log("wrong password");
  } else {
    console.log("correct pw");
  }
}

<input type="password" id="pw" oninput="checkpw(event, this)">

我建议将字段 Package 在窗体中。

**注意：**切勿在客户端上执行身份验证。

一个二个一个一个

function checkpw() {
  var x = document.getElementById("pw");
  var pw = "1234";
  if (x.value == pw) {
  //--------^ the variable x refers to the element itself. x.value is what you are looking for
      alert("correct pw");
  } else if(x.value == "") {
  //--------^ pw equals to "1234" which is the variable you created. replace pw with x.value instead (consider doing x.value.trim())
      alert("no password entered");
  } else {
      alert("wrong password");
  }
}

<input type="password" id="pw" />
<!---------------------^ I've added an id attribute since your code uses getElementById and that requires an id --->
<button onclick="checkpw()">Check password</button>