Binary Search Algorithm

binary-search.js

// Binary search
const bSearch = (list, number) => {
  // low and high keep track of which part of the list you’ll search in.
  let low = 0
  let high = list.length - 1

  // While you haven’t narrowed it down to one element …
  while (low <= high) {
    let mid = Math.floor((low + high) / 2)
    // … check the middle element.
    let guess = list[mid]

    if (guess === number) { // Found the item
      return mid
    } else if (guess > number) { // The guess was too high
      high = mid - 1
    } else { // The guess was too low
      low = mid + 1
    }
  }

  return null
}

console.log(bSearch([1, 3, 5, 7, 9], 9))
console.log(bSearch([1, 3, 5, 7, 9], 2))