使用简单的JavaScript创建下一个和上一个按钮？如果声明？

So I'm trying to do a simple back forward with a picture slider. I have gotten the next on the button, but need to create the function for back.

所以我试图用图片滑块做一个简单的后退。我已经在按钮上获得了下一个,但需要创建后退功能。

I cannot seem to get it and cannot remember with simple pure javascript. What would the if statement be? I assume the position needs to be changed to 0. Thank you for the advice.

我似乎无法得到它,也记不起简单的纯JavaScript。 if语句是什么?我认为这个职位需要改为0.谢谢你的建议。

For the forward I have:

对于前锋,我有:

  function Forward()
xxxx[arrayPosition].className = "thumb"; 
     mm[arrayPosition].className = "yyy"; 

        if(arrayPosition == xxxx.length - 1){
            arrayPosition = 0; }

          else{
           arrayPosition = arrayPosition + 1; in memory  }


        xxxx[arrayPosition].className = "thumb active";     
       mm[arrayPosition].className = "yyy active"; }

2 个解决方案

#1

When going back, you would want to check if the current arrayPosition is 0. If so, the array position should be updated to be the last index. For example:

返回时,您需要检查当前的arrayPosition是否为0.如果是,则应将阵列位置更新为最后一个索引。例如:

if(arrayPosition === 0) {
    arrayPosition = xxxx.length - 1;
} else {
    arrayPosition -= 1;
}

#2

try this

function Forward(){

     xxxx[arrayPosition].className = "thumb"; 
     mm[arrayPosition].className = "yyy"; 

        if((arrayPosition == xxxx.length - 1)||
           (arrayPosition == 0)){
            arrayPosition = 0; 
        }else{

            arrayPosition = arrayPosition + 1; 
        }


        xxxx[arrayPosition].className = "thumb active";     
       mm[arrayPosition].className = "yyy active"; 
       }