tiny-binary-search/index.js

Very small binary search index implimentation.

function BinarySearchIndex (values) {
  this.values = [].concat(values || []);
}

BinarySearchIndex.prototype.query = function (value) {
  var index = this.getIndex(value);
  return this.values[index];
};

BinarySearchIndex.prototype.getIndex = function getIndex (value) {
  if (this.dirty) {
    this.sort();
  }

  var minIndex = 0;
  var maxIndex = this.values.length - 1;
  var currentIndex;
  var currentElement;

  while (minIndex <= maxIndex) {
    currentIndex = (minIndex + maxIndex) / 2 | 0;
    currentElement = this.values[Math.round(currentIndex)];
    if (+currentElement.value < +value) {
      minIndex = currentIndex + 1;
    } else if (+currentElement.value > +value) {
      maxIndex = currentIndex - 1;
    } else {
      return currentIndex;
    }
  }

  return Math.abs(~maxIndex);
};

BinarySearchIndex.prototype.between = function between (start, end) {
  var startIndex = this.getIndex(start);
  var endIndex = this.getIndex(end);

  if (startIndex === 0 && endIndex === 0) {
    return [];
  }

  while (this.values[startIndex - 1] && this.values[startIndex - 1].value === start) {
    startIndex--;
  }

  while (this.values[endIndex + 1] && this.values[endIndex + 1].value === end) {
    endIndex++;
  }

  if (this.values[endIndex] && this.values[endIndex].value === end && this.values[endIndex + 1]) {
    endIndex++;
  }

  return this.values.slice(startIndex, endIndex);
};

BinarySearchIndex.prototype.insert = function insert (item) {
  this.values.splice(this.getIndex(item.value), 0, item);
  return this;
};

BinarySearchIndex.prototype.bulkAdd = function bulkAdd (items, sort) {
  this.values = this.values.concat([].concat(items || []));

  if (sort) {
    this.sort();
  } else {
    this.dirty = true;
  }

  return this;
};

BinarySearchIndex.prototype.sort = function sort () {
  this.values.sort(function (a, b) {
    return +b.value - +a.value;
  }).reverse();
  this.dirty = false;
  return this;
};

export default BinarySearchIndex;