如何获得 JavaScript 阶乘程序的循环以显示使用的工作？

Question

Hello there I have been challenged to write a program in JavaScript despite not really knowing much about it that asks the user for a number and then calculates the factorial of that number. I used already asked questions and managed to get the calculation to work but couldn't get the required output. I have to get it in the following output without using any fancy libraries or extra variables/arrays (which I can't think of how to do) :

(assuming user input is 5):

The factorial of 5 is 5*4*3*2*1=120 
OR
5! is  5*4*3*2*1=120 

Here is the code I've got so far:

 //prompts the user for a positive number var number = parseInt(prompt("Please enter a positive number")); console.log(number); //checks the number to see if it is a string if (isNaN(number)) { alert("Invalid. Please Enter valid NUMBER") } //checks the number to see if it is negaive else if (number < 0) { alert("Please Enter valid positive number"); } //if a positive integer is entered a loop is started to calculate the factorial of the number the user entered else { let factorial = 1; for (count = 1; count <= number; count++) { factorial *= count; } //Sends the inital number back to the user and tells them the factorial of that number alert("The factorial of " + number + " is " + factorial + "."); }

I know there are many similar questions to this as I looked around and used them to help me get this far but it is getting the output into the required format that I'm struggling with . I am told it is possible with a loop but don't know where to begin implementing that and I'm only allowed to use that solution.

Unfortunately this is part of a larger program in the challenge and I can only use the following variables:

Number (variable initialised as 0 to hold user input) Factorial (variable initialised to 1 to hold value of calculated factorial) Count (variable to hold number of times loop is executed for performing factorial calculation)

Answer 1

Probably you just need to build a string in that loop (on top of calculating the actual value):

 let input=parseInt(prompt("Number?")); let output=""; let result=1; for(let i=input;i>1;i--){ result*=i; output+=i+"*"; } console.log(input+"! is "+output+"1="+result);

The "no-array clause" in your task presumably means that you are not supposed to build an array and use join() on it, like

 let arr=[1,2,3,4,5]; console.log(arr.join("*"));

Answer 2

I have updated your code mainly here, Also make sure you are using the same variable num in your code and not number :

let factorials = [];
let result = 1;
for (count = num; count >= 1; count--) {
        result *=count;
        factorials.push(count);
}

 //prompts the user for a positive number var num = parseInt(prompt("Please enter a positive number")); console.log(num); //checks the number to see if it is a string if (isNaN(num)) { alert("Invalid. Please Enter valid NUMBER") } //checks the number to see if it is negaive else if (num < 0) { alert("Please Enter valid positive number"); } //if a positive integer is entered a loop is started to calculate the factorial of the number the user entered else { let factorials = []; let result = 1; for (count = num; count >= 1; count--) { result *=count; factorials.push(count); } //Sends the inital number back to the user and tells them the factorial of that number alert("The " + num + "! is " + factorials.join('*') + " is " + result + "."); }