binarySearch

src/dragAndDropHandler/binarySearch.ts

@@ -0,0 +1,27 @@
+function binarySearch<T>(items: T[], compareFn: (a: T) => number): null | T {
+    let low = 0;
+    let high = items.length;
+
+    while (low < high) {
+        const mid = (low + high) >> 1;
+        const item = items[mid];
+
+        if (item === undefined) {
+            return null;
+        }
+
+        const compareResult = compareFn(item);
+
+        if (compareResult > 0) {
+            high = mid;
+        } else if (compareResult < 0) {
+            low = mid + 1;
+        } else {
+            return item;
+        }
+    }
+
+    return null;
+}
+
+export default binarySearch;

src/dragAndDropHandler/index.ts

@@ -16,6 +16,7 @@ import { Node } from "../node";
 import NodeElement from "../nodeElement";
 import { getPositionName, Position } from "../position";
 import { getElementPosition } from "../util";
+import binarySearch from "./binarySearch";
 import DragElement from "./dragElement";
 import generateHitAreas from "./generateHitAreas";
 import { DropHint, HitArea } from "./types";
@@ -143,26 +144,15 @@ export class DragAndDropHandler {
             return null;
         }
 
-        let low = 0;
-        let high = this.hitAreas.length;
-        while (low < high) {
-            const mid = (low + high) >> 1;
-            const area = this.hitAreas[mid];
-
-            if (!area) {
-                return null;
-            }
-
+        return binarySearch<HitArea>(this.hitAreas, (area) => {
             if (y < area.top) {
-                high = mid;
+                return 1;
             } else if (y > area.bottom) {
-                low = mid + 1;
+                return -1;
             } else {
-                return area;
+                return 0;
             }
-        }
-
-        return null;
+        });
     }
 
     private generateHitAreas(): void {

src/test/dragAndDropHandler/binarySearch.test.ts

@@ -0,0 +1,31 @@
+import binarySearch from "../../dragAndDropHandler/binarySearch";
+
+it("returns null when the array is empty", () => {
+    const compareFn = (_item: number) => 0;
+
+    const result = binarySearch<number>([], compareFn);
+    expect(result).toBeNull();
+});
+
+it("finds a value", () => {
+    const compareFn = (item: number) => item - 5;
+
+    const result = binarySearch<number>([1, 5, 7, 9], compareFn);
+    expect(result).toEqual(5);
+});
+
+it("returns null when the value doesn't exist", () => {
+    const compareFn = (item: number) => item - 6;
+
+    const result = binarySearch<number>([1, 5, 7, 9], compareFn);
+    expect(result).toBeNull();
+});
+
+it("handles undefined values in the array", () => {
+    const compareFn = (item: number) => item - 6;
+    const array = [1, 5, 7, 9];
+    (array as any)[1] = undefined;
+
+    const result = binarySearch<number>(array, compareFn);
+    expect(result).toBeNull();
+});