Binary search text in Typescript

binarysearch_sting.ts

const binarySearch = (source_text: string, target: string): [number, string] | null => {
  const source_text_segments: string[] = (source_text.match(/[^.!?]+[.!?]+/g) || [source_text]).map(s => s.trim());
  const target_segment = target.trim();
  let result: [number, string] | null = null;
  let left: number = 0;
  let right: number = source_text_segments.length - 1;

  while (left <= right) {
    const mid = left + Math.floor((right - left) / 2);
    const segment = source_text_segments[mid];

    if (segment === target_segment) {
      result = [mid, segment];
      right = mid - 1;
    } else if (segment < target_segment) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }

  if (result) {
    let [firstIndex, firstSegment] = result;
    while (firstIndex > 0 && source_text_segments[firstIndex - 1] === firstSegment) {
      firstIndex--;
    }
    result = [firstIndex, firstSegment];
  }

  return result;
};