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外部javascript文件未加载

[英]external javascript file is not loading

我在home.html页面中包含了一个外部javascript文件“ check.js”,但似乎无法正常工作。 这是check.js的代码:

function required()
{   var empt=document.forms["form1"]["city_name"].value;
    if(empt=="")
    {
        alert("City name is required");
        return false;
    }
    return true;
}

而home.html的代码是:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Weather Forecast</title>
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" type="text/css" media="screen" href="/static/main.css" />
    <script src="check.js"></script>
    <link rel="shortcut icon" type="image/x-icon" href="/static/favicon.ico" />
</head>
<body>
    <p>
        <form name="form1" action='/weather' method="post" autocomplete="off" onsubmit="required()">
       <h1>City Name:</h1><input class="input1" type="text" name="city_name" onfocus="this.value=''" value="enter city name here....">  <br/>
        <input class="input2" type="submit" name="form" value="Submit">
        </form>
    </p>
</body>
</html>

怎么了??

在HTML文件中使用内联脚本:

<script>
    your code here
</script>

因为处理程序的返回值确定事件是否被取消,所以您需要更改此部分:

onsubmit="required()"

与:

onsubmit="return required()"

 function required(e) { var empt=document.forms["form1"]["city_name"].value; if(empt=="") { console.log("City name is required"); return false; } return true; } 
 <form name="form1" action='/weather' method="post" autocomplete="off" onsubmit="return required()"> <h1>City Name:</h1><input class="input1" type="text" name="city_name" onfocus="this.value=''" value="enter city name here...."> <br/> <input class="input2" type="submit" name="form" value="Submit"> </form> 

这里有一些问题。 首先,您不能在<p>元素内包含<form> <p>元素,因此您的HTML应该如下所示:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>Weather Forecast</title>
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <link rel="stylesheet" type="text/css" media="screen" href="/static/main.css" />
        <script src="check.js"></script>
        <link rel="shortcut icon" type="image/x-icon" href="/static/favicon.ico" />
    </head>
    <body>
        <form name="form1" action="/weather" method="post" autocomplete="off" onsubmit="required()">
            <h1>City Name:</h1><input class="input1" type="text" name="city_name" onfocus="this.value=''" value="enter city name here....">  <br/>
            <input class="input2" type="submit" name="form" value="Submit">
        </form>
    </body>
</html>

其次,您需要停止提交表单以便可以对其进行检查,但是如果可以,则需要将该表单提交到数据所在的位置。 要解决此问题,请使用提交按钮的onclick事件(而不是表单的onsubmit事件required()使required()触发。 还要添加一个e参数供以后使用:

<form name="form1" action="/weather" method="post" autocomplete="off">
    <h1>City Name:</h1><input class="input1" type="text" name="city_name" onfocus="this.value=''" value="enter city name here....">  <br/>
    <input class="input2" type="submit" name="form" value="Submit" onclick="required(e)">
</form>

您还需要input一个placeholder文本而不是一个value ,因此如果人们不触摸它,它实际上就不会被填充:

<input class="input1" type="text" name="city_name" onfocus="this.value=''" placeholder="enter city name here....">

然后使您的函数如下所示:

function required(event) {
    event.preventDefault();
    var empt=document.forms["form1"]["city_name"].value;
    if(!empt) {
        alert("City name is required");
        return;
    }
    document["form1"].submit();
}

现在应该可以了!

您编写的代码正在运行。 该警报永远不会显示,因为该值永远不会为空。 要解决此问题,请使用占位符属性代替输入元素中的值:

placeholder="enter city name here...."

固定:1-使用getElementByID 2-您有一个值集,也要对其进行测试3-将return添加到onsubmit

 function required() { let empt=document.getElementById("city_name").value; if(empt=="" || empt.includes("enter")) { //alert("City name is required"); return false } return true; } 
 <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>Weather Forecast</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" type="text/css" media="screen" href="/static/main.css" /> <script src="check.js"></script> <link rel="shortcut icon" type="image/x-icon" href="/static/favicon.ico" /> </head> <body> <p> <form name="form1" action='/weather' method="post" autocomplete="off" onsubmit="return required()"> <h1>City Name:</h1><input class="input1" type="text" id="city_name" name="city_name" onfocus="this.value=''" value="enter city name here...."> <br/> <input class="input2" type="submit" name="form" value="Submit"> </form> </p> </body> </html> 

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