# JavaScript: Find the nth ugly number

## JavaScript Math: Exercise-101 with Solution

Write a JavaScript program to find the nth ugly number.

Ugly numbers are positive numbers whose only prime factors are 2, 3 or 5. The first 10 ugly numbers are:
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, ...
Note: 1 is typically treated as an ugly number.

Visual Presentation:

Test Data:
(4) -> 4
(10) -> 12

Sample Solution:

JavaScript Code:

``````/**
* Function to find the nth ugly number.
* @param {number} num - The number of ugly numbers to find.
* @returns {number} - The nth ugly number.
*/
function test(num) {
result = [1]; // Initialize the array with the first ugly number, which is 1
x2 = x3 = x5 = 0; // Initialize pointers for multiples of 2, 3, and 5
while (result.length < num) { // Continue until the array contains the specified number of ugly numbers
m2 = result[x2] * 2; // Calculate the next multiple of 2
m3 = result[x3] * 3; // Calculate the next multiple of 3
m5 = result[x5] * 5; // Calculate the next multiple of 5
temp = Math.min(m2, m3, m5); // Find the smallest among the calculated multiples
if (temp === m2) { // If the smallest is the multiple of 2, move to the next multiple of 2
x2++;
}
if (temp === m3) { // If the smallest is the multiple of 3, move to the next multiple of 3
x3++;
}
if (temp === m5) { // If the smallest is the multiple of 5, move to the next multiple of 5
x5++;
}
result.push(temp); // Add the smallest ugly number to the result array
}
return result[num - 1]; // Return the nth ugly number
};

// Test cases
n = 4;
console.log("n = " + n);
console.log("nth Ugly number is " + test(n));

n = 10;
console.log("n = " + n);
console.log("nth Ugly number is " + test(n));
```
```

Output:

```n = 4
nth Ugly number is 4
n = 10
nth Ugly number is 12
```

Flowchart:

Live Demo:

See the Pen javascript-math-exercise-101 by w3resource (@w3resource) on CodePen.

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