Add insertionSort

snippets/insertionSort.md

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+---
+title: insertionSort
+tags: algorithm,array,intermediate
+---
+
+Sorts an array of numbers, using the insertion sort algorithm.
+
+- Use `Array.prototype.reduce()` to iterate over all the elements in the given array.
+- If the `length` of the accumulator is `0`, add the current element to it.
+- Use `Array.prototype.some()` to iterate over the results in the accumulator until the correct position is found.
+- Use `Array.prototype.splice()` to insert the current element into the accumulator.
+
+```js
+const insertionSort = arr =>
+  arr.reduce((acc, x) => {
+    if (!acc.length) return [x];
+    acc.some((y, j) => {
+      if (x <= y) {
+        acc.splice(j, 0, x);
+        return true;
+      }
+      if (x > y && j === acc.length - 1) {
+        acc.splice(j + 1, 0, x);
+        return true;
+      }
+      return false;
+    });
+    return acc;
+  }, []);
+```
+
+```js
+insertionSort([6, 3, 4, 1]); // [1, 3, 4, 6]
+```