Javascript 当我运行这段代码时，它给了我错误的信息：login.js:12 uncaughttypeerror:cannotreadproperty'；价值'；HTMLInputElement.login（login.js:12）处的空值

查看您的代码，必须是

getuser

或

getpassword

设置为null。因此，

localStorage.getItem（“用户名”）

或

localStorage.getItem（“用户名”）返回null

let username = document.querySelector("username");
let password = document.querySelector("password");
let singinBtn = document.querySelector("sing_in");
let getuser = localStorage.getItem("username");
let getpassword = localStorage.getItem("password");

if(singinBtn){
    singinBtn.addEventListener("click",login);

    function login(e){
        e.preventDefault();

        if(getuser.value==="" || getpassword.value===""){
            alert("please fill data");
        }
        else{ 
            if(getuser && getuser.trim===username.value.trim() && getpassword && getpassword.trim===password.value.trim())
            {
                setTimeout(()=>{ 
                    window.location="index.html";
                },1500);
            }
            else{
                alert("username or password wrong");
            }
        }
    }
}