1st Attempt - JavaScript Binary Search (Done in Lagos Traffic!)

js-BST

let binarySearch = (haystack, needle) => {
  let allNums = haystack.every( entry => !isNaN(entry) );
  let needleIsNum = !isNaN(needle);

  if( needleIsNum && allNums){
    // prepare inputs
    haystack = haystack.sort( (a, b) => a - b );

    // define Algol
    let bSearchr = (aHaystack) => {
      let stackLen = aHaystack.length;
      let midIndex = Math.floor( stackLen / 2 );
      let midItem = aHaystack[ midIndex ];

      console.log("%s items, [%s] in the middle @ index %s", stackLen, midItem, midIndex);

      if(needle === midItem){
        let found = haystack.indexOf(needle);
        console.log("matched needle %s @ %s", needle, found);
        return found;
      }

      // We can't just keep reducing the array.
      // At some point, with a tiny array,
      // very likely to contain our "needle",
      // we can "search" for "needle".
      // Also need an algorithmic way
      // to dtermine 3.
      if(stackLen <= 3){
        let found = haystack.indexOf(needle);
        console.log("found needle %s @ %s", needle, found);
        return found;
      }

      let start = -1, end = -1;
      if(needle < midItem){
        start = 0;
        end = midIndex;
        console.log('branching left ...');
      }else if (needle > midItem){
        start = midIndex + 1;
        end = stackLen;
        console.log('branching right ...');
      }

      let aReducedHaystack = aHaystack.slice(start, end);
      return bSearchr(aReducedHaystack);
    };

    let found = bSearchr(haystack);
    console.log("Found %s @ index %s in [%s]", needle, found, haystack.join(", "));
    return found;
  }

};