cube-iterator-behavior.js

import {dedupingMixin} from "@polymer/polymer/lib/utils/mixin.js";

/**
 * @polymerBehavior
 * @type {{iterate: CubeIteratorBehavior.iterate}}
 */
export const CubeIteratorBehavior = dedupingMixin(superClass => {
  class CubeIteratorBehavior extends superClass {
    iterate(arr, callback)
    {
      let i, superClass,
        classType = /\[object (.+)]/.exec(Object.prototype.toString.call(arr))[1];
      switch(classType)
      {
        case 'String':
          superClass = '';
          break;
        case 'Array':
          superClass = [];
          break;
        case 'Object':
          superClass = {};
          break;
        default:
          superClass = new classType.constructor;
      }
      for(i in arr)
      {
        if(arr.hasOwnProperty(i) && !superClass.hasOwnProperty(i))
        {
          let retVal = callback(arr[i], i, arr);
          if(typeof(retVal) !== 'undefined')
          {
            return retVal;
          }
        }
      }
    }
  }

  return CubeIteratorBehavior;
});