javascript - 我如何创建一个倒数计时器，用户输入任何数字并将其从该数字显示为零？

Question

如何创建倒数计时器，其中用户以秒为单位输入时间并在javascript中从该数字显示为零？

var userChoice = parseInt(prompt("Type in time to countdown")); 
var timer = setInterval(countDown, 1000); 

// this is what i have 
function countDown() { 
   console.log(counter); 
   counter--; 
   if (counter < 0) { 
      clearInterval(timer); 
      console.log("END"); 
   }
}

Answer 1

计时器只触发一次。确保将以下行放在 countDown 函数的末尾，以便再次调用它：

timer = setTimeout(countDown, 1000); 

Answer 2

您的错误是：counter从未定义。将其替换为userChoice它可以按照您的方式完美运行：

var userChoice = parseInt(prompt("Type in time to countdown")); 
var timer = setInterval(countDown, 1000); 

function countDown() { 
   console.log(userChoice); 
   userChoice--; 
   if (userChoice < 0) { 
      clearInterval(timer); 
      console.log("END"); 
   }
}