阶乘函数返回未定义

Question

This a simple code for factorial, I have written the function and it loops through giving right output but at the end, it returns undefined. I don't know why.

function factorial(n){
    let value=1; 
    for(let i=1;i<=n;i++) {
        value = i*value; 
        console.log(value); 
    }  
}

Answer 1

Because you do not return anything from the function, so undefined is the result of its work. You need to return the value explicitly:

function factorial(n){
  let value=1;

  for(let i=1;i<=n;i++) {
    value = i*value; 
    console.log(value); 
  } 

  return value;
}

Answer 2

You can find factorial by using recursion. Here is the implementation.

 function factorial(x){ if(x == 0) //Exit condition return 1; return x * factorial(x-1); //5*4*3*2*1 } console.log(factorial(5));

Answer 3

This is good implementation:

const factorial = n => n > 1 ? n * factorial(--n) : 1;

And your function does not have return , so it returns undefined ;