Binary search function to find the note in an array sorted by frequency that is closest to the one passed as a parameter

frequencyBinarySearch.js

// 'notes' is an array of objects like { note: 'A4', frequency: 440 }.
// See initialization in the source code of the demo
var findClosestNote = function(freq, notes) {
  // Use binary search to find the closest note
  var low = -1, high = notes.length;
  while (high - low > 1) {
      var pivot = Math.round((low + high) / 2);
      if (notes[pivot].frequency <= freq) {
          low = pivot;
      } else {
          high = pivot;
      }
  }
  
  if(Math.abs(notes[high].frequency - freq) <= Math.abs(notes[low].frequency - freq)) {
      // notes[high] is closer to the frequency we found
      return notes[high];
  }
  
  return notes[low];
};