HTML Input Checkbox required用法及代碼示例

HTML DOM中的Input Checkbox required屬性用於設置或返回在提交表單之前是否應檢查輸入複選框字段。此屬性用於反映HTML必需屬性。

用法:

它返回Input Checkbox required屬性。
```
checkboxObject.required
```
它用於設置“輸入複選框”必需屬性。
```
checkboxObject.required = true|false
```

屬性值：它包含以下列出的兩個屬性值：

true:它用於指定提交表單之前必須選中的複選框。
false:它具有默認值。它指定在提交表單之前不得選中該複選框。

返回值：它返回一個布爾值，該值表示在提交表單之前必須選中該複選框。

範例1：本示例返回Input Checkbox required屬性。

<!DOCTYPE html> 
<html>  
    <head>  
        <title> 
            DOM Input Checkbox required Property 
        </title> 
    </head>  
      
    <body style = "text-align:center;">  
      
        <h1 style = "color:green;"> 
            GeeksforGeeks 
        </h1>  
          
        <h2>DOM Input Checkbox required Property</h2>  
          
        <form >  
          
            <!-- Below input elements have attribute "required" -->
            <input type="checkbox" name="check" id="GFG"
                    value="1" required>Checked by default<br>  
                      
            <input type="checkbox" name="check" value="2"> 
                    Not checked by default<br>  
        </form> <br> 
          
        <button onclick="myGeeks()"> 
            Submit 
        </button> 
          
        <p id="sudo" style="color:green;font-size:30px;"></p> 
          
        <!-- Script to use required property -->
        <script> 
            function myGeeks() { 
                var g = document.getElementById("GFG").required; 
                document.getElementById("sudo").innerHTML = g; 
            } 
        </script> 
    </body>  
</html>

輸出：
在單擊按鈕之前：

單擊按鈕後：

範例2：本示例設置“輸入複選框”必填屬性。

<!DOCTYPE html> 
<html>  
    <head>  
        <title> 
            DOM Input Checkbox required Property 
        </title> 
    </head>  
      
    <body style = "text-align:center;">  
      
        <h1 style = "color:green;"> 
            GeeksforGeeks 
        </h1>  
          
        <h2>DOM Input Checkbox required Property</h2> 
          
        <form >  
            <!-- Below input elements have attribute 
                    "required" -->
            <input type="checkbox" name="check" id="GFG"
                    value="1" required>Checked by default<br>  
                      
            <input type="checkbox" name="check" value="2"> 
                    Not checked by default<br>  
        </form> <br> 
          
        <button onclick="myGeeks()"> 
            Submit 
        </button> 
          
        <p id="sudo" style="color:green;font-size:20px;"></p> 
          
        <!-- Script to set Input Checkbox required Property -->
        <script> 
            function myGeeks() { 
                var g = document.getElementById("GFG").required 
                        = "false"; 
                          
                document.getElementById("sudo").innerHTML 
                        = "The value of the required attribute" 
                          + " was changed to " + g; 
            } 
        </script> 
    </body>  
</html>

輸出：
在單擊按鈕之前：

單擊按鈕後：

支持的瀏覽器：DOM輸入支持的瀏覽器所需複選框的屬性如下所示：

穀歌瀏覽器
Internet Explorer 10.0
Firefox
Opera
Safari

相關用法

注：本文由純淨天空篩選整理自ManasChhabra2大神的英文原創作品 HTML | DOM Input Checkbox required Property。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。