Question

我需要知道代码var的含义以及代码var focusname=""和var msg=" ";的作用及其用途，它是我评估的一部分，我需要知道我是允许使用帮助，我是HTML的新手。

非常感谢任何帮助

    <title>Exam entry</title>
<script language="javascript" type="text/javascript">
window.onload=function(){
window.validateForm=function() {
    var result = true;
    var msg = "";
    var focusname="";
    if (document.ExamEntry.name.value == "") {
        msg += "You must enter your name \n";
        focusname="name";
        //document.ExamEntry.name.focus();
        document.getElementById('name1').style.color = "red";
        //result = false;
    }
    if (document.ExamEntry.subject.value == "") {
        msg += "You must enter the subject \n";
       // document.ExamEntry.subject.focus();
        if (focusname=="")
        {
        focusname="subject";
        }
        document.getElementById('subject1').style.color = "red";
        //result = false;
    }
    var Number = document.ExamEntry.Exam_Number.value
    if (Number == "") {
        msg += "You must enter the exam Number \n";
        //document.ExamEntry.Exam_Number.focus();
        if (focusname=="")
        {
        focusname="Exam_Number";
        }
        document.getElementById('Exam_Number1').style.color = "red";
        //result = false;
    }else if (Number.length != 4) {
        msg += "You must enter at least Four Numbers in the Exam Number \n";
         if (focusname=="")
        {
        focusname="Exam_Number";
        }
        //document.ExamEntry.Exam_Number.focus();
        document.getElementById('Exam_Number1').style.color = "red";
        //result = false;
    }
else if (isNaN(Number)) {
        msg += "You must enter at least four numeric characters in the Exam Number feild \n";
     if (focusname=="")
        {
        focusname="Exam_Number";
        }   
    // document.ExamEntry.Exam_Number.focus();
        document.getElementById('Exam_Number1').style.color = "red";
        //result = false;
    }
    var valchecked = '';
    var len = document.getElementsByName('examtype').length;

    for (i = 0; i < len; i++) {

if ( document.ExamEntry.examtype[i].checked ) {

valchecked = document.ExamEntry.examtype[i].value;
 break;

}

}
    if (valchecked == '') {
        msg += "Select Exam Type";
        document.getElementById('Exam_Type').style.color = "red";
         if (focusname=="")
        {
        focusname="examtype_GCSE";
        }

    } 

    if (msg != ""){
        alert(msg)
        document.getElementById(focusname).focus();
        return false;
    }else{
        return confirm('You have chosen ' + valchecked + ' is this correct?');
    }

}
}//]]>  

</script>


</head>
<body>
  <h1>Exam Entry Form</h1>
<form name="ExamEntry" method="post" action="success.html">
<table width="50%" border="0">
<tr>
<td id="name1">Name</td>
<td><input type="text" name="name"  id="name" /></td>
</tr>
<tr>
<td id="subject1">Subject</td>
<td><input type="text" name="subject" id="subject"/></td>
</tr>
<tr>
<td id="Exam_Number1">Exam Number</td>
<td><input type="text" name="Exam_Number" id="Exam_Number" ><font size="3">(Maximum characters: 4)</font> </td>
</tr>
<tr>

<table><form action="">
<td id="Exam_Type">Exam Type</td>
<tr><td><input type="radio" id="examtype_GCSE" name="examtype" value="GCSE" /> : GCSE<br /></tr>
<tr><td><input type="radio" id="examtype_AS" name="examtype" value="AS"/> : AS<br /></tr>
<tr><td><input type="radio" id="examtype_A2" name="examtype" value="A2" /> : A2<br /></tr>
<tr><td><input type="submit" name="Submit" value="Submit" onclick="return validateForm();" /></td>
<td><input type="reset" name="Reset" value="Reset" /></td>
</tr>
</table>
</form>

</body>


</html>

Answer 1

var用于在javascript中声明变量。

var msg="";表示您声明了变量msg，该变量为空且与focusname相同。

有关var

的更多信息

Answer 2

使用var关键字声明变量，如下所示：

前 - var msg; //multi line declaration var focusname;

var msg, focusname; //Single line declaration

这里，msg＆amp; focusname是保存值的变量名。

var关键字仅用于声明。

JavaScript是一种动态类型语言。这意味着JavaScript变量可以保存任何数据类型的值。

与许多其他语言不同，您不必在变量声明期间告诉JavaScript变量将包含哪种类型的值。变量的值类型可以在程序执行期间发生变化，JavaScript会自动处理它。

var在Javascript中意味着什么？

2 个答案: