Question

我试图在JavaScript中编写一个实现此提示的程序

编写JavaScript函数 COUNTDOWN（ⅰ）它接受一个整数参数并从i返回一个\ countdown“到0，其间出现一个空格每个号码。例如，countDown（5）应返回字符串“5 4 3 2 1 0”。至于第一个问题，你可以想在计算机上测试你的解决方案。

sofar我有这个

var i= "";

function countdown(i)

{

    while( i > 0)

    {
        console.log(integer);
        i--;
    }
}
countdown();

有人可以帮我编程

Answer 1

希望这有足够的意义：

function countdown(i) {
    //initialize the variable to be returned with the initial i
    var ret = i;
    //in each iteration, assigns i to i-1 then checks if i >= 0
    while (--i >= 0) {
        //concatenates a space and the current i value to the return string
        ret += ' ' + i;
    }
    //returns the string
    return ret;
}

Fiddle

Answer 2

我希望您阅读我在代码中添加的评论并学习。

// you write comments in JavaScript with two forward slashes
// i is the integer parameter of your countdown function
// i is passed to countdown when called, i.e. countdown(9)
function countdown(i)    
{
    // this is an ret string variable that is private to the countdown function
    // you can't access ret from outside of this function
    var ret = "";   

    // your loop should include 0 according to your requirements
    while( i >= 0)
    {
        // here you are appending i to your ret string which you'll return at the end of this function      
        ret += i;// += is a short hand form of saying ret = ret + i

        // you want to append an empty space for every i except the last one (0)
        if(i > 0) {
            ret += " "; 
        }
        i--;    // here you are decrementing i
    }
    return ret;
}
// here you are making the actual call to the function with integer 5 
// you are assigning the returned value of your function call to result variable
var result = countdown(5);  

// here you are printing your result string variable to the log
console.log(result);

这里使用递归的另一种解决方案（更高级），替代for / while循环，其中函数调用自身：

// here is an implementation using recursion
function countdown(i)    
{
    if(i<=0)    
        return i;
    return i + " " + countdown(--i);
}

Answer 3

您希望在倒计时中加入0，以便

while (i >= 0)

而不是while (i > 0)，最后会排除0。

另外，正如上面提到的一些评论，var i = ""将i定义为字符串，因此您无法执行i--之类的操作。您应该将i定义为整数，例如var i = 5。

Answer 4

以下是答案：

 function countdown(i) {
   answer = '';
   while( i >= 0) {
      answer = answer + i.toString() + ' ';
      i--;
   }
   return answer;
 }

 countdown(5);

Answer 5

以下是使用递归的方法：

//define countdown function
var countdown = function countdown(i) {
    //loop while the passed in parameter "i" is >= 0
    while (i >= 0) {
        //return a space concatenated with the value of i
        //and call the countdown function again (by
        //concatenating the result) to continue counting down
        return ' ' + i + countdown(i -= 1);
    }
    return ''; //out of loop, return an empty string
};
console.log(countdown(5));

Answer 6

递归方式;）

var countdown=function(i) {
    console.log(i);
    i>0 && countdown(i-1);
}
    countdown(10);

JavaScript倒计时程序

6 个答案: