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qwerty
Asked: 2020-02-08 17:39:58 +0800 CST 2020-02-08 17:39:58 +0800 CST

Calculate the factorial of a number and print the process

  • 772

I have code that calculates the factorial of a number in JavaScript, but what I want it to display are the numbers just like in the image.

var n = 5,
  t = 1,
  q = document.querySelector('.n');


for (i = 0; i < n; i++) {
  t = t * (n - i);
}

q.innerHTML = (n + '! = ' + t);
<span class="n"></span>

enter image description here

javascript

2 Answers

  1. You can create a buffer that stores the numbers while you calculate the result:

    let n = 5,
  t = 1,
  q = document.querySelector('.n'),
  b = '';


for (let i = n; i > 0; i--) {
  if (i !== 1) {
    b += i + ' x ';
  } else {
    b += i;
  }
  t *= i;
}
q.innerHTML = (n + '! = ' + b + ' = ' + t);
    <span class="n"></span>

    Or you can use ES6 functions

    const n = 5;
const array = Array.from({length: n}, (x,i) => i+1);
const process = array.reverse().join(' x ');
const factorial = array.reduce((x, y) => x*y, 1)
const result = `${n}! = ${process} = ${factorial}`;
document.getElementById('result').innerHTML = result;
    <span id="result"></span>

    Documentation:

    • 2
  2. Best Answer

    You can concatenate the value and then use the substring to remove the last concatenated value which in this case would be X

    var n = 5,
t = 1,
q = document.querySelector('.n');
var concat = '';

for (i = 0; i < n; i++) {
    t = t * (n - i);
    concat += n-i+' x ';
}

var factorial = concat.substring(0, concat.length - 3);

q.innerHTML = (n + '! = '+ factorial +' = ' + t);
    <span class="n"></span>

    • 1