# How to Calculate the Median of an Array of Numbers in JavaScript?

## Calculating the median of a JavaScript array of numbers

You can calculate the median of an array of numbers in JavaScript in the following steps:

1. Sort the array in ascending order;
2. Determine the median, which would be one of the following:
1. Element at the middle index if the array has an odd number of elements, or;
2. Average of the two elements at the middle indexes if the array has an even number of elements.

For example, you can implement this in the following way:

```function median(arr) {
// 1: sort array in ascending order
const sortedArr = arr.sort();
const middleIndex = arr.length / 2;
// 2.1: if odd, return middle element
if (arr.length % 2 !== 0) {
return arr[Math.floor(middleIndex)];
}
// 2.2: if even, return average of two middle elements
return (arr[middleIndex - 1] + arr[middleIndex]) / 2;
}

console.log(median([1, 2])); // 1.5
console.log(median([4, 1, 7])); // 4
console.log(median([3, 7, 5, 1, 8, 9])); // 6
console.log(median([39, 3, 14, 29, 23, 13, 23, 23, 40, 23, 21, 5, 7, 12, 56])); // 23
```

For arrays with an odd length, rounding down the middle index (i.e. `Math.floor(middleIndex)` is needed because dividing an odd array length by `2` would yield a fraction.

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