# JavaScript: Calculate how many numbers in the given array are less or equal to the given value using the percentile formula

## JavaScript fundamental (ES6 Syntax): Exercise-167 with Solution

Write a JavaScript program to calculate how many numbers in the given array are less than or equal to the given value. This is done using the percentile formula.

Use Array.prototype.reduce() to calculate how many numbers are below the value and how many are the same value and apply the percentile formula.

**Sample Solution:**

**JavaScript Code:**

```
// Define a function 'percentile' that calculates the percentile of a given number in an array
const percentile = (arr, num) => (arr.filter((item) => item <= num).length / arr.length) * 100;
// Calculate and log the percentile of the number 5 in the array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
console.log(percentile([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 5)) // 50;
// Calculate and log the percentile of the number 10 in the array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
console.log(percentile([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 10)) // 100;
// Calculate and log the percentile of the number 3 in the array [1, 2, 3, 4, 5, 6]
console.log(percentile([1, 2, 3, 4, 5, 6],3)) // 50;
// Calculate and log the percentile of the number 4 in the array [1, 2, 3, 4, 5, 6]
console.log(percentile([1, 2, 3, 4, 5, 6],4)) // 66.66;
```

Output:

50 100 50 66.66666666666666

**Flowchart:**

**Live Demo: **

See the Pen javascript-basic-exercise-167-1 by w3resource (@w3resource) on CodePen.

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