# Merge sort

Isabelle Viktoria Maciohsek · JavaScript, Algorithm, Array, Recursion · Dec 27, 2020

Sorts an array of numbers, using the merge sort algorithm.

• Use recursion.
• If the `length` of the array is less than `2`, return the array.
• Use `Math.floor()` to calculate the middle point of the array.
• Use `Array.prototype.slice()` to slice the array in two and recursively call `mergeSort()` on the created subarrays.
• Finally, use `Array.from()` and `Array.prototype.shift()` to combine the two sorted subarrays into one.
```const mergeSort = arr => {
if (arr.length < 2) return arr;
const mid = Math.floor(arr.length / 2);
const l = mergeSort(arr.slice(0, mid));
const r = mergeSort(arr.slice(mid, arr.length));
return Array.from({ length: l.length + r.length }, () => {
if (!l.length) return r.shift();
else if (!r.length) return l.shift();
else return l[0] > r[0] ? r.shift() : l.shift();
});
};```
`mergeSort([5, 1, 4, 2, 3]); // [1, 2, 3, 4, 5]`

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