JavaScript |评论

注释用于阻止语句的执行。编译器执行代码时会忽略注释。注释是用户友好的，因为用户可以使用注释获得代码的解释。

句法：

// For single line comment

/* For block of lines comment
...
...
*/

返回值：在代码执行期间，注释被忽略。

示例 1：此示例说明了使用 // 的单行注释。

html

  

    
        JavaScript Comments
    
      
    
          
        // Function to add two numbers
        function add() {
              
            // Declare three variables
            var x, y, z;
              
            // Input a number and store it into variable x
            x = Number( document.getElementById("num1").value );
              
            // Input a number and store it into variable x
            y = Number( document.getElementById("num2").value );
              
            // Sum of two numbers
            z= x +y;
              
            // Return the sum
            document.getElementById("sum").value = z;
        }
    

  

    Enter the First number: 
    Enter the Second number: 
      
    
        Sum
    
      
    

  

输出：
在点击按钮之前：

点击按钮后：

示例 2：此示例说明使用 /* ... */ 的多行注释

html

  

    
        JavaScript Comments
    
      
    
      
        /* Script to get two input from user
        and add them */
        function add() {
              
            /* Declare three variable */
            var x, y, z;
              
            /* Input the two nos. num1, num2
            Input num1 and store it in x
            Input num2 and store it in y
            The sum is stored in a variable z*/
            x = Number(document.getElementById("num1").value); 
            y = Number(document.getElementById("num2").value);
            z = x + y;
              
            document.getElementById("sum").value = z;
        }
    

  

    Enter the First number : 
    Enter the Second number: 
      
    
        Sum
    
      
    

  
                    

输出：
在点击按钮之前：

点击按钮后：

示例 3：此示例说明注释代码永远不会执行。

html

  

    
        JavaScript Comments
    
      
    
          
        function add() {
              
            var x, y, z;
              
            x = Number( document.getElementById("num1").value );
              
            y = Number( document.getElementById("num2").value );
              
            z= x +y;
              
            // Comment the code section
            //document.getElementById("sum").value = z;
        }
    

  

    Enter the First number: 
    Enter the Second number: 
      
    
        Sum
    
      
    

  
                    

输出：
在点击按钮之前：

点击按钮后：