I wrote this, as a refresher, better keep it just in case…

bsearch.ts

// The output should be the "difference" between each inputs, thus 0 mean identical.
type ComparatorFunction = <Type>(lookup: Type, pointer: Type ) => number

function bsearch<Type>(
  dictionary: Array<Type>,
  lookup: Type,
  comparator: ComparatorFunction,
  startIndex: number = 0,
  endIndex: number = dictionary.length-1,
): Array<Type> {
  if (startIndex>endIndex) return [];

  const pivot = Math.floor((startIndex+endIndex)/2)

  const comparison = comparator(lookup, dictionary[pivot])

  if( comparison === 0 ) return [dictionary[pivot]];

  return comparison > 0 ?
    bsearch(dictionary, lookup, comparator, startIndex, pivot-1)
    : bsearch(dictionary, lookup,comparator, pivot+1, endIndex)
}