Question

例如，如果用户在上一个文本框中输入5，则该用户只能在下一个输入中输入大于7的数字，因为在上一个输入和下一个输入之间，我需要至少2个数字或更大的数字，否则帮助我。

<!doctype html> 
<html> 
<head> </head> 
<body> 
<form action="../" onsubmit="return checknumber(this);">
 <input type="number" name="year1" size="20" maxlength="20"> <br> <br> 
<input type="number" name="year2" size="20" maxlength="20"> <br> 
<input type="SUBMIT" value="Send Address!">
</form>

 <script> function checknumber(theForm) { 
if (theForm.year1.value > theForm.year2.value) { 
alert('Those enter more than 2'); return false;
 } else { return true; }
 } 
</script>
 </body>
 </html>

Answer 1

我为您发布了新答案，您可以根据需要进行更新。您可能还需要参考Javascript tutorial，这可能有助于轻松学习HTML的JavaScript。

尝试以下：

function checknumber() {   
 var txt1=parseInt(document.getElementsByName('year1')[0].value);
 var txt2=parseInt(document.getElementsByName('year2')[0].value);
 var lblErr=document.getElementById('lblForYearError');
 if(txt2<(txt1+2))
 {
    lblErr.textContent='Value is less then +2'
 }
 else if(txt2>(txt1+2))
 {
     lblErr.textContent='Value is more then +2'
 }
 else
 {
     lblErr.textContent='';
 }
 
}

<!doctype html> <html>
    <head> </head> 
    <body> 
        <form action="../" onsubmit="return checknumber(this);">            <input type="number" name="year1" size="20" maxlength="20">                                           <br> <br>
       <input type="number" name="year2" size="20" maxlength="20" oninput="checknumber(this);"><label id='lblForYearError' style='font-color:red;'></label>
       <br> 
       <input type="SUBMIT" value="Send Address!">
       </form>  </body> 
       </html>

Answer 2

您将要评论自己的答案。

只需要改善您的if条件并将数据从string解析为int，

请从theForm.year1.value > theForm.year2.value更改if (theForm.year2.value != (theForm.year1.value+2))：

尝试以下：

function checknumber(theForm) {   
 if (parseInt(theForm.year2.value) != (parseInt(theForm.year1.value)+2)) 
    { 
    alert('Those enter more than 2');
            return false;
            } 
     return true;
            
}

<!doctype html> <html>
    <head> </head> 
    <body> 
        <form action="../" onsubmit="return checknumber(this);">            <input type="number" name="year1" size="20" maxlength="20">                                           <br> <br>
       <input type="number" name="year2" size="20" maxlength="20">
       <br> 
       <input type="SUBMIT" value="Send Address!">
       </form>  </body> 
       </html>

与上一个和下一个输入字段比较

2 个答案: