Binary search

typescript/binary-search/binary-search.ts

@@ -0,0 +1,19 @@
+export function find(
+  haystack: number[],
+  needle: number,
+  start: number = 0,
+  end: number = haystack.length - 1
+): number | never {
+  if (start > end || end < start) {
+    throw new Error("Value not in array");
+  }
+  const index = start + Math.floor((end - start) / 2);
+  const value = haystack[index];
+  if (needle > value) {
+    return find(haystack, needle, index + 1, end);
+  }
+  if (needle < value) {
+    return find(haystack, needle, start, index - 1);
+  }
+  return index;
+}