查找 JavaScript 对象的长度

方法一：使用 Object.keys() 方法： Object.keys() 方法用于将对象属性名称作为数组返回。 length 属性用于获取对象中存在的键的数量。它给出了对象的长度。

句法：

objectLength = Object.keys(exampleObject).length

例子：

  

    Length of a JavaScript object

  

    GeeksforGeeks
      
    Length of a JavaScript object
      
    
        exampleObject = {
            id: 1,
            name: 'Arun',
            age: 30
        }
    
      
    
        Click on the button to get
        the length of the object.
    
      
    
        Length of the object is: 
        
    
  
    
        Get object length
    
      
    
        function getObjectLength() {
              
            // Declare an object
            exampleObject = {
                id: 1,
                name: 'Arun',
                age: 30
            }
  
            // Using Object.keys() method to get length
            objectLenght = Object.keys(exampleObject).length;
  
            document.querySelector('.output').textContent
                    = objectLenght;
        }
    

  
                    

输出：

• 在点击按钮之前：
  
• 点击按钮后：
  

方法二：遍历对象的所有字段并检查其属性： hasOwnProperty() 方法用于返回一个布尔值，表示对象是否具有指定的属性作为自己的属性。此方法可用于检查每个键是否存在于对象本身中。循环遍历对象的内容，如果存在键，则键的总数会增加。这给出了对象的长度。

句法：

var key, count = 0;

// Check if every key has its own property
for (key in exampleObject) {
    if (exampleObject.hasOwnProperty(key))

        // If the key is found, add it to the total length
        count++;
}
objectLenght = count;

例子：

  

    Length of a JavaScript object

  

    GeeksforGeeks
      
    Length of a JavaScript object
      
    
        exampleObject = {
            id: 1,
            name: 'Arun',
            age: 30,
            department: 'sales'
        }
    
      
    
        Click on the button to get
        the length of the object.
    
      
    
        Length of the object is:
        
    
  
    
        Get object length
    
      
    
        function getObjectLength() {
  
            // Declare an object
            exampleObject = {
                id: 1,
                name: 'Arun',
                age: 30,
                department: 'sales'
            }
  
            var key, count = 0;
  
            // Check if every key has its own property
            for (key in exampleObject) {
                if (exampleObject.hasOwnProperty(key))
  
                    // If key is found, add it
                    // to total length
                    count++;
            }
            objectLenght = count;
  
            document.querySelector('.output').textContent
                    = objectLenght;
        }
    

  
                    

输出：

• 在点击按钮之前：
  
• 点击按钮后：
  

JavaScript 以网页开发而闻名，但它也用于各种非浏览器环境。您可以按照这个 JavaScript 教程和 JavaScript 示例从头开始学习 JavaScript。