feat: Add helper to determine closest number in an array.

templates/helpers/closestNumber.ts

@@ -0,0 +1,18 @@
+/**
+ * Returns the number in the array that is closest to the target number.
+ */
+export const closestNumber = (numbers: number[], target: number): number => {
+  let closestNumber: number | null = null;
+  let closestDistance = Infinity;
+
+  for (let i = 0; i < numbers.length; i++) {
+    const distance = Math.abs(numbers[i] - target);
+
+    if (distance < closestDistance) {
+      closestNumber = numbers[i];
+      closestDistance = distance;
+    }
+  }
+
+  return closestNumber as number;
+};