HTML Input Checkbox required用法及代码示例

HTML DOM中的Input Checkbox required属性用于设置或返回在提交表单之前是否应检查输入复选框字段。此属性用于反映HTML必需属性。

用法:

它返回Input Checkbox required属性。
```
checkboxObject.required
```
它用于设置“输入复选框”必需属性。
```
checkboxObject.required = true|false
```

属性值：它包含以下列出的两个属性值：

true:它用于指定提交表单之前必须选中的复选框。
false:它具有默认值。它指定在提交表单之前不得选中该复选框。

返回值：它返回一个布尔值，该值表示在提交表单之前必须选中该复选框。

范例1：本示例返回Input Checkbox required属性。

<!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>

输出：
在单击按钮之前：

单击按钮后：

范例2：本示例设置“输入复选框”必填属性。

<!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>

输出：
在单击按钮之前：

单击按钮后：

支持的浏览器：DOM输入支持的浏览器所需复选框的属性如下所示：

谷歌浏览器
Internet Explorer 10.0
Firefox
Opera
Safari

相关用法

注：本文由纯净天空筛选整理自ManasChhabra2大神的英文原创作品 HTML | DOM Input Checkbox required Property。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。