basicprimitives/src/algorithms/mergeSort.js

Basic Primitives Diagrams for JavaScript - data visualization components library that implements organizational chart and multi-parent dependency diagrams, contains implementations of JavaScript Controls and PDF rendering plugins.

/**
 * Callback function to measure item weights of merged arrays.
 * 
 * @callback getItemWeightCallback
 * @param {object} item The item to weight
 * @returns {number} Returns item's weight.
 */

/**
 * Merges array of sorted arrays into one using call back function for comparison.
 * 
 * @param {object[][]} arrays  Array of sorted arrays of objects.
 * @param {getItemWeightCallback} getItemWeight Callback function to measure item weight. 
 * @param {boolean} ignoreDuplicates If true returns distinct weight items only.
 * @returns {object[]} Returns merged sorted array.
 */
export default function mergeSort(arrays, getItemWeight, ignoreDuplicates) {
  var result = null,
    firstArray, secondArray, mergedArray, arrayIndex,
    firstIndex, secondIndex, firstLen, secondLen, firstItem, secondItem,
    firstItemWeight, secondItemWeight,
    currentValue;

  switch (arrays.length) {
    case 0:
      result = [];
      break;
    default:
      firstArray = [];
      for (arrayIndex = 0; arrayIndex < arrays.length; arrayIndex += 1) {
        secondArray = arrays[arrayIndex];
        mergedArray = [];

        firstLen = firstArray.length;
        secondLen = secondArray.length;

        firstIndex = 0;
        secondIndex = 0;

        firstItem = null;
        firstItemWeight = null;
        secondItem = null;
        secondItemWeight = null;

        if (firstLen > 0) {
          firstItem = firstArray[firstIndex];
          firstItemWeight = !getItemWeight ? firstItem : getItemWeight(firstItem);
        }

        if (secondLen > 0) {
          secondItem = secondArray[secondIndex];
          secondItemWeight = !getItemWeight ? secondItem : getItemWeight(secondItem);
        }
        currentValue = null;
        while (firstIndex < firstLen || secondIndex < secondLen) {

          if (firstIndex >= firstLen) {
            if (!ignoreDuplicates || currentValue != secondItem) {
              mergedArray.push(secondItem);
              currentValue = secondItem;
            }
            secondIndex += 1;


            if (secondIndex < secondLen) {
              secondItem = secondArray[secondIndex];
              secondItemWeight = !getItemWeight ? secondItem : getItemWeight(secondItem);
            }
          } else {
            if (secondIndex >= secondLen) {
              if (!ignoreDuplicates || currentValue != firstItem) {
                mergedArray.push(firstItem);
                currentValue = firstItem;
              }
              firstIndex += 1;


              if (firstIndex < firstLen) {
                firstItem = firstArray[firstIndex];
                firstItemWeight = !getItemWeight ? firstItem : getItemWeight(firstItem);
              }
            } else {
              if (firstItemWeight < secondItemWeight) {
                if (!ignoreDuplicates || currentValue != firstItem) {
                  mergedArray.push(firstItem);
                  currentValue = firstItem;
                }
                firstIndex += 1;

                if (firstIndex < firstLen) {
                  firstItem = firstArray[firstIndex];
                  firstItemWeight = !getItemWeight ? firstItem : getItemWeight(firstItem);
                }
              } else {
                if (!ignoreDuplicates || currentValue != secondItem) {
                  mergedArray.push(secondItem);
                  currentValue = secondItem;
                }
                secondIndex += 1;

                if (secondIndex < secondLen) {
                  secondItem = secondArray[secondIndex];
                  secondItemWeight = !getItemWeight ? secondItem : getItemWeight(secondItem);
                }
              }
            }
          }
        }
        firstArray = mergedArray;
      }
      result = firstArray;
      break;
  }
  return result;
};