# JavaScript: Find the n^{th} ugly number

## JavaScript Math: Exercise-101 with Solution

Write a JavaScript program to find the n^{th} 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.

**Visualisation:**

**Test Data:**

(4) -> 4

(10) -> 12

**Sample Solution:**

**HTML Code:**

```
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JavaScript program to Find the nth ugly number</title>
</head>
<body>
</body>
</html>
```

**JavaScript Code:**

```
function test(num) {
result = [1]
x2=x3=x5=0
while (result.length<n){
m2 = result[x2]*2
m3 = result[x3]*3
m5 = result[x5]*5
temp = Math.min(m2,m3,m5)
if(temp===m2){
x2++
}
if(temp===m3){
x3++
}
if(temp===m5){
x5++
}
result.push(temp)
}
return result[n-1]
};
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));
```

Sample 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.

**Improve this sample solution and post your code through Disqus**

**Previous:** Check a given number is an ugly number or not.

**Next:** Count total number of 1s from 1 to N.

**What is the difficulty level of this exercise?**

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## JavaScript: Tips of the Day

**Shorten an array using its length property**

A great way of shortening an array is by redefining its length property.

let array = [0, 1, 2, 3, 4, 5, 6, 6, 8, 9] array.length = 4 // Result: [0, 1, 2, 3]

Important to know though is that this is a destructive way of changing the array. This means you lose all the other values that used to be in the array.

Ref: https://bit.ly/2LBj213

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