# Calculating h index of a citation in JavaScript

Suppose we have an array of positive integers that represents the number of citations a particular researcher has conducted over a period of time.

We are required to write a JavaScript function that takes in one such array and the function should find the h-index of that researcher based on the citations data represented by the array.

## H-Index:

Consider a researcher who performed N number of citations in his career. Then the researcher has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each.

For example −

If the citations array is −

const arr = [1, 6, 3, 0, 5];

This data represents that the researcher has 5 papers in total and each of them had received 1, 6, 3, 0, 5 citations respectively.

And since the researcher has 3 papers with at least 3 citations each and the remaining two with no more than 3 citations each, the h-index is 3.

Therefore, the output for this array should be −

const output = 3;

## Example

Following is the code −

const arr = [1, 6, 3, 0, 5];
const findHIndex = (arr = []) => {
let possible = [];
let { length: len } = arr;
if (len === 0){
return 0;
};
possible.length = len + 2;
possible = possible.join('-').split('').map(() => 0);
for (let i = 0; i < len; i ++) {
let val = arr[i];
let ind = val > len ? len : val;
possible[ind] += 1;
}
let result = 0;
for (let k = len; k >= 0; k --) {
result += possible[k];
if (result >= k) {
return k;
}
}
};
console.log(findHIndex(arr));

## Output

Following is the console output −

3