en/builder/src/echarts3/util/array/nest.js

import * as zrUtil from 'zrender/src/core/util';
/**
 * nest helper used to group by the array.
 * can specified the keys and sort the keys.
 */

export default function nest() {
  var keysFunction = [];
  var sortKeysFunction = [];
  /**
   * map an Array into the mapObject.
   * @param {Array} array
   * @param {number} depth
   */

  function map(array, depth) {
    if (depth >= keysFunction.length) {
      return array;
    }

    var i = -1;
    var n = array.length;
    var keyFunction = keysFunction[depth++];
    var mapObject = {};
    var valuesByKey = {};

    while (++i < n) {
      var keyValue = keyFunction(array[i]);
      var values = valuesByKey[keyValue];

      if (values) {
        values.push(array[i]);
      } else {
        valuesByKey[keyValue] = [array[i]];
      }
    }

    zrUtil.each(valuesByKey, function (value, key) {
      mapObject[key] = map(value, depth);
    });
    return mapObject;
  }
  /**
   * transform the Map Object to multidimensional Array
   * @param {Object} map
   * @param {number} depth
   */


  function entriesMap(mapObject, depth) {
    if (depth >= keysFunction.length) {
      return mapObject;
    }

    var array = [];
    var sortKeyFunction = sortKeysFunction[depth++];
    zrUtil.each(mapObject, function (value, key) {
      array.push({
        key: key,
        values: entriesMap(value, depth)
      });
    });

    if (sortKeyFunction) {
      return array.sort(function (a, b) {
        return sortKeyFunction(a.key, b.key);
      });
    } else {
      return array;
    }
  }

  return {
    /**
     * specified the key to groupby the arrays.
     * users can specified one more keys.
     * @param {Function} d
     */
    key: function (d) {
      keysFunction.push(d);
      return this;
    },

    /**
     * specified the comparator to sort the keys
     * @param {Function} order
     */
    sortKeys: function (order) {
      sortKeysFunction[keysFunction.length - 1] = order;
      return this;
    },

    /**
     * the array to be grouped by.
     * @param {Array} array
     */
    entries: function (array) {
      return entriesMap(map(array, 0), 0);
    }
  };
}