Question

好的，所以我不熟悉HTML中的整个Javascript。所以，我一直在研究一个简单的登录程序。由于某种原因，我的功能不起作用。每次我输入正确的用户名和密码时，它都会告诉我“您输入的用户名或密码不正确！”

<html>
    <head>
    <title>Login info stuff</title>
    </head>
    <body>
    <script type="text/javascript">
    var username = document.write("<input type='text' name='Username'>");
    document.write("<br />");
    var password = document.write("<input type='password' name='Password'>");
    document.write("<br />");
    function correct(){
    if(username==="Username" & password==="Password")
    {location="blank.HTML"}
    else{alert("You entered your Username or Password incorrectly!")}
    }
    Submit = document.write("<input type='submit' value='Login' onClick='correct()'>");
    </script>
    </body>
</html>

Answer 1

那是因为您比较的用户名和密码变量不是文本框中的值。这应该有效：

<html>
    <head>
        <title>Login info stuff</title>
    </head>
    <body>
        <script type="text/javascript">
            document.write("<input type='text' name='Username' id='username'>");
            document.write("<br />");
            document.write("<input type='password' name='Password' id='password'>");
            document.write("<br />");

            function correct(){
                if(document.getElementById('username').value ==="Username" && document.getElementById('password').value === "Password")
                {
                    location="blank.HTML";
                }
                else{
                    alert("You entered your Username or Password incorrectly!")
                }
             }
             Submit = document.write("<input type='submit' value='Login' onClick='correct()'>");
    </script>
    </body>
</html>

我在这里做了什么：

在两个字段中添加了id
比较值时，首先通过调用document.getElementById获取DOM元素，然后从value属性中获取当前值

Answer 2

username和password变量存储document.write的返回值。他们没有检索到这些值。为此，您需要：

document.write("<input type=\"text\" name=\"username\" id=\"username\">");
var username = document.getElementById('username').value;

所以你的脚本应该是：

<script type="text/javascript">
    document.write("<input type='text' name='Username' id='username'>");
    document.write("<br />");
    document.write("<input type='password' name='Password' id='password'>");
    document.write("<br />");


    function correct(){
        if(document.getElementById('username').value==="Username" && document.getElementById('password').value==="Password")
        {
            location="blank.HTML"
        } else {
            alert("You entered your Username or Password incorrectly!")
        }
    }

    Submit = document.write("<input type='submit' value='Login' onClick='correct()'>");
</script>

Answer 3

AND在JavaScript中是＆amp;＆amp;

此外，您还需要将输入值保存为变量，如：

var user = document.getElementById('username').value;
var pwd = document.getElementById('password').value;

然后将这两个变量用于if语句

编辑：要使用getElementById()，首先需要在document.write行的相应输入中添加ID

Answer 4

<html>
    <head>
    <title>Login info stuff</title>
    </head>
    <body>
    <form id="myform" name="myform" action="blank.html" >
      <input type="text" name="username" id="username" />
      <input type="password" name="password" id="password" />
      <input type="submit" name="submit" id="submit" value="Login" onclick="return correct();" />
    </form>

    <script type="text/javascript">
    var username = document.getElementById("username"),
        password = document.getElementById("password"),
        myform = document.getElementById('myform');

    function correct() {
        if(username.value!=="username" || password.value!=="password") {
          alert("You entered your Username or Password incorrectly!");
          return false;
        } else {
          myform.submit();
        }
    }
    </script>
    </body>
</html>

重新设计了一下 http://plnkr.co/edit/iHDlTW5726g8NqHIjz1A?p=preview

登录帮助 - if语句不起作用？

4 个答案: