getBinarySearch() - Takes an array of values and returns a function that can be used to carry out the binary search on those values.

getBinarySearch.js

/**
 * Takes an array of values and returns a function that can be used to
 * carry out the binary search on those values.  The returned function
 * takes one argument to indicate which direction the desired value may
 * be found (send a negative number to look further back, a positive
 * number to look further ahead or a `0` to return the same value as
 * before).  It doesn't matter what value you pass the first time you
 * call the returned function.
 * @template T
 * @param {T[]} values
 * @returns {(direction: number) => {index: number, value: T, values: T[]}}
 */
function getBinarySearch(values) {
  let index, min = 0, max = values.length - 1;
  return function(direction) {
    const isFirstRun = index === undefined;
    if (isFirstRun) direction = 0;
    if ((direction !== 0 && index >= 0) || isFirstRun) {
      if (direction > 0) min = index + 1;
      else if (direction < 0) max = index - 1;
      index = min > max ? -1 : Math.floor((max + min) / 2);
    }
    return {index, value: values[index], values};
  };
}