text: /* Concat multiple arrays into a single array.
   *
   * |Name  |Type |Desc              |
   * |------|-----|------------------|
   * |...arr|array|Arrays to concat  |
   * |return|array|Concatenated array|
   */
  
  /* example
   * concat([1, 2], [3], [4, 5]); // -> [1, 2, 3, 4, 5]
   */
  
  /* module
   * env: all
   * test: all
   */
  
  /* typescript
   * export declare function concat(...args: Array<any[]>): any[];
   */
  
  _('toArr');
  
  exports = function() {
      const args = toArr(arguments);
      let ret = [];
  
      for (let i = 0, len = args.length; i < len; i++) {
          ret = ret.concat(toArr(args[i]));
      }
  
      return ret;
  };
  