text: (function() {
    'use strict';
    window._ = {};
  
    _.chunk = (array, size) => {
      const len = array.length;
      const store = [];
      for (let i = 0; i < len; i += size) {
        const chunk = array.slice(i, i + size);
        store.push(chunk);
      }
      return store;
    };
  
    _.compact = (array) => {
      return _.filter(array, elem => Boolean(elem));
    };
  
    _.concat = (...args) => {
      return _.reduce(args, (acc, next, i, arr) => {
        if (Array.isArray(next)) {
          acc.push(...next);
        } else {
          acc.push(next);
        }
        return acc;
      }, []);
    };
  
  })();
  