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[英]Uncaught TypeError: Cannot read properties of null (reading 'addEventListener') in javaScript
[英]Cannot read properties of null (reading 'addEventListener') in a Javascript file (not script tag)
我是 JavaScript 初學者,當我使用 VSCode 制作 HTML、CSS、JS 項目時,遇到以下錯誤:
未捕獲的類型錯誤:無法讀取 null 的屬性(在“addEventListener”處讀取)
另外,我的項目是:只使用 JavaScript 字典和一個 logged_in 變量創建一個登錄 + 注冊系統(如果它是假的,它將把人們重定向到注冊頁面)
HTML 注冊文件:
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8'>
<meta http-equiv='X-UA-Compatible' content='IE=edge'>
<title>BeedHub Register</title>
<meta name='viewport' content='width=device-width, initial-scale=1'>
<link rel='stylesheet' type='text/css' media='screen' href='style.css'>
<script src='index.js'></script>
</head>
<body>
<h1 class="hello_world">Welcome!</h1>
<p class="aaa">We're so excited to see you!</p>
<div class="usernamediv">
<input id="main_usr" placeholder="Write username here" type="text">
</div>
<div class="passworddiv">
<input id="main_pw" placeholder="Write password here" type="password">
</div>
<div class="btn">
<button id="main_register">Register!</button>
</div>
<div class="login_instead">
<a href="C:\Users\directory\.vscode\directory\directory\directory\login">Login Instead</a>
</div>
</body>
</html>
JavaScript 文件:
// Variables
var db = {
};
var logged_in = false;
// Register Elements
var rg_usr = document.getElementById("main_usr");
var rg_pw = document.getElementById("main_pw");
var rg_submit = document.getElementById("main_register");
// Event Listeners
rg_submit.addEventListener('click',function() {
if (db[rg_usr.innerHTML]) {
var error_usr_taken = document.createElement("p");
error_usr_taken.innerHTML = "Error: Username Already Taken!";
} else if (rg_usr.innerHTML == "" || null) {
var error_usr_none = document.createElement("p");
error_usr_none.innerHTML = "Error: Username is null!";
} else if (rg_pw.innerHTML == "" || null) {
var error_pw_none = document.createElement("p");
error_pw_none.innerHTML = "Error: Password is null!";
} else {
db[rg_usr.innerHTML] = rg_pw.innerHTML;
logged_in = true;
window.location.pathname = "/successpage";
};
});
如果您希望我提供更多信息,請通過 ping 評論。
PS I have also used the script tag on my /login/index.html file, but the web says that multiple HTML files using the same JavaScript file have no problem.
提前致謝,
乖巧的
您的腳本在頁面上的標記之前執行,這就是您收到錯誤的原因。
因此,您可以像這樣在body
的最后移動script
標簽:
<body>
<!-- All contents here -->
<script src='index.js'></script>
</body>
或者您可以將defer
添加到您的 script 標簽並讓它繼續在head
中,如下所示:
<script src='index.js' defer></script>
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