更改时间时如何更改下拉菜单？

任务是在更改时间时更改下拉菜单。下面讨论两种方法。

方法一：使用setTimeOut()方法，一段时间后执行切换菜单的代码。

示例：此示例实现了上述方法。

  

    
        How to change dropdown 
        menu when time is changed?
    
  
    
    

  

    
        GeeksForGeeks
    
  
    
  
    
        GFG1
        GFG2
        GFG3
        GFG4
        GFG5
    
    
  
    
        Click here
    
      
    
    
    
        var elUp = document.getElementById("GFG_UP");
        var elDown = document.getElementById("GFG_DOWN");
        elUp.innerHTML = "Click on the button "
            + "to change the dropdown list "
            + "after 4 seconds";
        $('button').click(function () {
            setTimeout(
                function () {
                    $("#select option[value=1]")
                                .text('GFG_N');
                    elDown.innerHTML 
                        = "Drop-down menu changed";
                }, 4000);
        })        
    

  

输出：

方法 2：使用Date()方法获取当前的DateTime对象，然后在菜单将被更改时使用setSeconds()和getSeconds()方法声明另一个 DateTime 对象。

示例：此示例实现了上述方法。

  

    
        How to change dropdown 
        menu when time is changed?
    
  
    
    

  

    
        GeeksForGeeks
    
    
    
    
        GFG1
        GFG2
        GFG3
        GFG4
        GFG5
    
    
    
    
        Click here
    
    
    
    
        var elUp = document.getElementById("GFG_UP");
        var elDown = document.getElementById("GFG_DOWN");
        elUp.innerHTML = "Click on the button to "
                + "change the dropdown list after "
                + "5 seconds of current time";
        $('button').click(function () {
            var d1 = new Date();
            var d2 = new Date();
            d2.setSeconds(d1.getSeconds() + 5);
            setTimeout(
                function () {
                    $("#select option[value=1]")
                                    .text('GFG_N');
                    elDown.innerHTML 
                        = "Drop-down menu changed";
                }, d2 - d1);
        })        
    

  

输出：