w3resource

JavaScript: Find the number of times to replace a given number with the sum of its digits until it convert to a single digit number

JavaScript Basic: Exercise-105 with Solution

Write a JavaScript program to find the number of times to replace a given number with the sum of its digits until it convert to a single digit number.

Pictorial Presentation:

JavaScript: Find the number of times to replace a given number with the sum of its digits until it convert to a single digit number.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Find the number of times to replace a given number with the sum of its digits until it convert to a single digit number</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function digit_to_one(num) {

    var digitSum = function(num) {

        var digit_sum = 0;
        while (num) {
            digit_sum += num % 10;
            num = Math.floor(num / 10);
        }

        return digit_sum;
    };

    var result = 0;

    while (num >= 10) {
        result += 1;
        num = digitSum(num);
    }

    return result;
}

console.log(digit_to_one(123))
console.log(digit_to_one(156))

Sample Output:

1
2

Flowchart:

Flowchart: JavaScript - Find the number of times to replace a given number with the sum of its digits until it convert to a single digit number

ES6 Version:

function digit_to_one(num) {

    const digitSum = num => {

        let digit_sum = 0;
        while (num) {
            digit_sum += num % 10;
            num = Math.floor(num / 10);
        }

        return digit_sum;
    };

    let result = 0;

    while (num >= 10) {
        result += 1;
        num = digitSum(num);
    }

    return result;
}

console.log(digit_to_one(123))
console.log(digit_to_one(156))

Live Demo:

See the Pen javascript-basic-exercise-105 by w3resource (@w3resource) on CodePen.


Contribute your code and comments through Disqus.

Previous: Write a JavaScript program to find two elements of the array such that their absolute difference is not greater than a given integer but is as close to the said integer.
Next: Write a JavaScript program to divide an integer by another integer as long as the result is an integer and return the result.

What is the difficulty level of this exercise?



JavaScript: Tips of the Day

Parameter's value

function getItems(fruitList, ...args, favoriteFruit) {
  return [...fruitList, ...args, favoriteFruit]
}

getItems(["banana", "apple"], "pear", "orange")

...args is a rest parameter. The rest parameter's value is an array containing all remaining arguments, and can only be the last parameter! In this example, the rest parameter was the second parameter. This is not possible, and will throw a syntax error.

function getItems(fruitList, favoriteFruit, ...args) {
  return [...fruitList, ...args, favoriteFruit];
}


getItems(['banana', 'apple'], 'pear', 'orange');
The above example works. This returns the array [ 'banana', 'apple', 'orange', 'pear' ].

Ref: https://bit.ly/3jFRBje