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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.


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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.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04