Min Heap Implementation

As an exercise, I wanted to implement a min heap using JavaScript.

I'm not terribly familiar with JavaScript best practices, so I wanted to get feedback on my approach.

Notes

• I decided to implement the min heap using an array.
  
  
  
  
  • I filled the first element with a null value to make some of the math a little easier (in my opinion) - I know this is slightly more memory, but I thought the tradeoff was worth it
  
  
  
  


• The actual MinHeap function is effectively a factory function (and not a constructor) that creates objects representing min heaps that wraps the underlying array implementation in closure.
  
  
  
  
  • The idea here was to minimize the public API (i.e. "privatize" as much of the internal implementation details as possible).
  
  
  • I explicitly named functions so that if any errors occurred, it would be easier to identify in the stack trace - I don't know if this preferred / matters
  
  
  
  


• In the future, I could see this heap implementation expanding past a min heap to take a custom comparator, but I decided to keep it simple for the time being and simply use <.


• I decided to write this in ES5 - I'll probably refactor this to use ES6 conventions in the future.

Questions

The questions I have are

1. Is the factory function approach sound?


2. Are there any JavaScript best practices that I've violated or ignored?


3. Is my implementation flawed in any way?

Implementation

var MinHeap = function() {

  var values = [null];



  function getParentIndex(childIndex) {

    return Math.floor(childIndex / 2);

  }



  function getChildIndices(parentIndex) {

    var leftChild = parentIndex * 2;



    return {

      leftChild: leftChild,

      rightChild: leftChild + 1,

    };

  }



  function swap(firstIndex, secondIndex) {

    var firstValue = values[firstIndex];



    values[firstIndex] = values[secondIndex];

    values[secondIndex] = firstValue;

  }



  function getSmallestNode(firstIndex, secondIndex) {

    var firstValue = values[firstIndex];

    var secondValue = values[secondIndex];



    if (firstValue > secondValue) {

      return {

        value: secondValue,

        index: secondIndex,

      };

    }



    return {

      value: firstValue,

      index: firstIndex,

    };

  }



  function add(value) {

    var valueIndex,

        parentIndex,

        parentValue;



    values.push(value);



    valueIndex = getSize();

    parentIndex = getParentIndex(valueIndex);

    parentValue = values[parentIndex];



    while (parentValue > value && parentIndex >= 1) {

      swap(parentIndex, valueIndex);



      valueIndex = parentIndex;

      parentIndex = getParentIndex(valueIndex);

      parentValue = values[parentIndex];

    }

  }



  function remove() {

    var firstValue = values[1],

        lastValueIndex = values.length - 1,

        lastValue = values.splice(lastValueIndex, 1)[0];



    if (getSize() > 0) {

      values[1] = lastValue;

      lastValueIndex = 1;



      var childIndices = getChildIndices(lastValueIndex);

      var smallestNode = getSmallestNode(childIndices.leftChild, childIndices.rightChild);



      while (lastValue > smallestNode.value) {

        swap(lastValueIndex, smallestNode.index);

        lastValueIndex = smallestNode.index;



        var childIndices = getChildIndices(lastValueIndex);

        smallestNode = getSmallestNode(childIndices.leftChild, childIndices.rightChild);

      }

    }



    return firstValue;

  }



  function getFirst() {

    return values[1];

  }



  function getSize() {

    return values.length - 1;

  }



  return {

    add: add,

    remove: remove,

    getFirst: getFirst,

    getSize: getSize,

  };

};