我想编写javascript代码以获得额外的倒计时

Question

so basically this the prompt:

Addition countdown

you enter a number and the code should be adding a number while countingdown, for example if the user enter 10, then the result should be: 10 + 9 + 8 + 7 + 6 + 5 + 4 +3 +2 +1=55 .

This is what I have so far:

var num = Number(prompt("Enter a Number Greater than zero"));

while (num > 0){

    first = num;

    second = num-=1;

    document.write(first +  " +" + second + " +");

    value = first + num;

    document.write(value)
    num--;
}

but I keep on getting something like this: 4 +3 +72 +1 +3 ( let's say 4 is the number the user inputs )

I'm stuck can someone please help me????!!

Answer 1

You could change the algorithm a bit, because for the first value, you need no plus sign for the output.

 var num = Number(prompt("Enter a Number Greater than zero")), value = 0; document.body.appendChild(document.createTextNode(num)); value += num; num--; while (num > 0) { document.body.appendChild(document.createTextNode(' + ' + num)); value += num; num--; } document.body.appendChild(document.createTextNode(' = ' + value)); 

Answer 2

You can keep total in one variable outside of while loop.

 var num = Number(prompt("Enter a Number Greater than zero")); var total = 0; while (num > 0) { total += num; document.body.innerHTML += (num == 1 ? num + ' = ' + total : num + ' + '); num--; }