(misc): converting binary search to typescript (#2129)

src/utils/binary-search.ts

@@ -0,0 +1,44 @@
+type BinarySearchComparison < T > = (candidate: T) => -1 | 0 | 1;
+
+const BinarySearch = {
+
+  /**
+   * Searches for an item in an array which matches a certain condition.
+   * This requires the condition to only match one item in the array,
+   * and for the array to be ordered.
+   *
+   * @param {Array<T>} list The array to search.
+   * @param {BinarySearchComparison<T>} comparisonFn
+   *      Called and provided a candidate item as the first argument.
+   *      Should return:
+   *          > -1 if the item should be located at a lower index than the provided item.
+   *          > 1 if the item should be located at a higher index than the provided item.
+   *          > 0 if the item is the item you're looking for.
+   *
+   * @return {T | null} The object if it is found or null otherwise.
+   */
+  search: function<T> (list: T[], comparisonFn: BinarySearchComparison<T>): T | null {
+    let minIndex: number = 0;
+    let maxIndex: number = list.length - 1;
+    let currentIndex: number | null = null;
+    let currentElement: T | null = null;
+
+    while (minIndex <= maxIndex) {
+      currentIndex = (minIndex + maxIndex) / 2 | 0;
+      currentElement = list[currentIndex];
+
+      let comparisonResult = comparisonFn(currentElement);
+      if (comparisonResult > 0) {
+        minIndex = currentIndex + 1;
+      } else if (comparisonResult < 0) {
+        maxIndex = currentIndex - 1;
+      } else {
+        return currentElement;
+      }
+    }
+
+    return null;
+  }
+};
+
+export default BinarySearch;